Gelatin is an animal byproduct. Nonetheless, I know many self-identified vegetarians who eat gelatin anyway. Are there reasons for being vegetarian (e.g. religious) that allow the consumption of gelatin?
The other rationale for eating something like gelatin, e.g. Amonium phosphatides, Magnesium Stearate, Carmine, Lipase, is that animal derived additives are everywhere. They often occur in small amounts in processed foods. In the past, as a practical matter, I didn't worry about animal derived additives. At that time, I didn't have the shopping skills to identify the additives and find alternatives. So by this reasoning, a package of Jello is not allowable, but a processed food with gelatin as the 10th ingredient would be okay, on the grounds of being practical. By this sort of rule, you'd probably be eating grams a year of animal products.
This is summed up here:
Gelatin is not vegetarian and is certainly not vegan. Sadly, millions of vegetarians and vegans could actually be using animal commodities unknowingly as the list of products that contain gelatin seems to grow everyday. Be certain to only buy certified vegan, animal-safe body products and make sure to read your food labels!
Fortunately, there are vegetarian alternatives to classic gelatin, such as Agar, Carrageenan and Vegan Jel. More details can be found here.
So shortly put, the main reason for a vegetarian to eat classic gelatin seems to be not knowing about it (its presence in the food / how it is obtained). As a consequence, some vegetarians certainly eat gelatin.
I am a vegetarian, and I have no issue with consuming gelatin. My reason for being vegetarian is because meat doesn't taste pleasant to my palate.
Concerning the usage of the words vegetarian and vegan, by definition gelatin is not any of the two, so the question is moot.
On the other hand when it comes to an ethical framework based on morals frequently taken as the reason for veg*anism, I can argue in favour of gelatin, to a degree.
The argument applies to several reasons for living veg*n, for example not wanting to exploit animals and trying to limit the ecological impact one makes. I make the case that in those cases, it doesn't follow from your morals (when you include at least self-preservation as a moral good too) that you can't use animal product so that in some cases, it is justified to use them. Gelatin may sometimes be such a case.
Following moral goals is equivalent to minimizing the ways in which you act against those moral goals. For practically relevant morals such as those concerned here, you can't always follow them, which is why phrasing them as above is useful. Examples of how you can't follow them are plentiful: If you give anyone money (in exchange for anything) whom you know not to follow your morals, you are supporting them in not following your morals and acting against your own morals. If you live in a house, consider the whole dependency tree of a house (land, work, building supplies, work creating the building supplies, supplies for creating the building supplies and so on recursively) and the myriad ways this kills/harms animals and the negative ecological impact this has. If you sometimes use cars or planes instead of going on foot, hell, if you use a bike instead of going on foot or use shoes instead of going barefoot. You probably don't do this consciously, but you are continuously balancing self preservation (or egoism, and can you even tell where the line between two is, exactly?) and your other morals.
Now that we have established that this is not about absolutes, it should also be clear that compromises are possible. You have to act against your morals, so you choose the least evils.
And sometimes, such a least evil can be to just buy something which looks morally-okay enough to you (but not completely okay) but which has other advantages which can make this a zero net moral implications trade off or even a positive one.
Buying (or even just eating) things which contain small amounts of animal matter, or using (but not buying or otherwise contributing to demand for the product) even high-animal content products can almost always be at least a zero net effect trade off.
Gelatin-containing foods are sometimes like this: They don't contain much gelatin and gelatin being a byproduct of meat production which could be replaced relatively cheaply means you are not driving slaughtering demand up much: If the animals wouldn't be slaughtered anyway, it would be cheaper to use something else than gelatin (the producer would, too because after all they are capitalists). On the other hand if gelatin demand was lower than the amount which can be provided by the amount of animal slaughtering going on anyway, those byproducts would like just be thrown away or used for something less productive.
So for example when you have apple juice of cost x$ versus vegan apple juice of cost 2x$ then it's very sensible to just buy the apple juice which is not certified vegan (but might very well be anyway) because even if gelatin is actually used for clearing it, the amount won't be large and you are free to use that money (and time you saved searching for the vegan one) for something which more than offsets the negative impact you (may have) had.
And in answer to the comment about vegan cheese: Well, this is difficult because with all my claims, I never have numbers to back it up and it's very hard to put stuff like this in numbers anyway (consider the huge dependency trees of most stuff you buy and it's obvious why). For gelatin, you don't need numbers because even with worst case estimates, its negative impact can still reasonably be offset. Cheese takes a large amount of milk to make, and milk is no byproduct but the primary product of the milk industry. So if you are thinking about fondue or cheese and bread eaten like this, then it's unlikely that it's easy to compensate for eating it. One scenario in which it would be possible is if the vegan cheese was much more expensive not because you are feeding the coffers of some capitalist (as in "vegan apple juice"), but because it's really that expensive. Expensive things generally have large dependency trees (somewhere, that money is being spent) and thus a large negative impact on the environment and like that on animals, too (extinctions because of climate change, etc.).
I could also argue against this (for example from a more idealist standpoint), but it remains a valid point.
intentional ignorance (as a self chosen exception) - "at least the rest of this cake is vegetarian, and whoever paid for it didn't understand the issue..."
just plain old ignorance - some people might not realize that something that comes as transparent sheets or white powder (it certainly looks manufactured) is an animal product
plain old being misled - the consumption of gelatin in some winemaking is not that well known about outside of serious vegetarian circles, and the use as fortification carrier substances in fortified juices etc even less...
considering it a byproduct that has no significant contribution to the meat economy if bought and consumed (probably wrong, just as with leather)
being vegetarian due to taste/aesthetic reasons and plainly not having an issue with this ingredient
I’m a vegetarian, and I eat gelatin. Simply because I feel bad eating meat (I guess morally) so I don’t eat it. It’s a lot easier to eat something yummy like lollies (which is when I eat it.) and just not think about the fact that it contains meat. Obviously I only occasionally eat lollies so it’s not a huge deal. Also, saying I’m vegetarian- to me, is just a way of telling people that I don’t eat meat. Maybe I’m not technically vegetarian because I eat lollies, but it’s easier than saying “oh I don’t eat meat. No I’m not a vegetarian, I eat lollies”. It’s just a way of explaining your dietary requirements so that people are able to cater to your needs.