The claim here is that veganism isn't worth joining because vegans are judgmental
This is a blanket statement that attempts to describe a small class of people, of which you've met a handful. That sounds pretty judgmental.
However, let's assume, in the best case, that this is a position that isn't just something that a carnist picked up from other carnists telling them that vegans are judgmental (because it's an easy dodge) but is an informed conclusion from a number of vegans they already met. The obvious problem with this statement is that it's a classic toupée fallacy, because it's highly likely that they've met vegans that were so non-judgmental that they simply had no idea.
You accidentally proved yourself wrong if you make this argument. If you had reasons to be against veganism, then you'd say it. But you can't simultaneously say "I'm mad at you for your attitude towards my unethical choices" and "They aren't unethical". Either carnism is ethical or it's not. If it is, then you wouldn't say this, you'd say "Vegans are wrong", not "Vegans are judgmental", and if it is unethical, then you're agreeing with the vegans. But you can't have your cake and eat it too.
Given all the ridiculous comments that carnists make such as "How do you know someone is vegan" or the use of the term "soyboy", etc. it would be very difficult to see how this isn't merely some sort of projection or other caricature of the vegan position. Isn't having the presupposition that "all vegans are judgemental" in fact a judgmental position itself?!
Most vegans that I've run into don't nearly beat carnists over the head with personal attacks as much as the opposite, but of course, this is anecdotal evidence, just as much as vegans being judgmental. Neither position proves anything about the argument of whether or not it's ethical to slaughter an animal.
If you want to make ethical choices make them, no one is forcing you to use the label vegan if you feel like you're forced into joining some club. You just happen to be a person that boycotts the use of animal products but doesn't use any labels. And anyway, labels are just linguistic shortcuts that make it so you don't need to reexplain everything each time. If you don't want to use one, that's on you.
Not some imagined motivation of the arguers. The reason to ditch carnism is that it hurts animals, humans, the environment, and yourself. Anything else is white noise.