Vegans are preachy and annoying
Sometimes true, and entirely beside the point. The manner of an argument's delivery has no bearing on whether it holds.
Vegans often treat ordinary meals as moral battlegrounds, lecturing friends, family and strangers who never asked and casting everyone who eats meat as complicit in cruelty. That kind of sanctimony is grating, and it reasonably makes people wary of a movement whose members seem more interested in feeling superior than in persuading anyone. When the people pushing a view routinely behave this way, it is fair to doubt the view deserves the hearing they demand for it.
Some advocacy is self-defeating, and there is a reasonable conversation about tactics: moralising tends to produce defensiveness rather than reflection, which is an argument about effectiveness rather than about truth.
As a response to the position, it addresses the wrong object. Whether animal agriculture is justified does not vary with how pleasant its critics are. The generalisation is also drawn from a skewed sample: people mentioning their diet unprompted are more memorable than the large majority who never raise it, so the visible cases are selected precisely for being the irritating ones.
Attacking the person advancing an argument rather than the argument itself. Their character has no bearing on whether their reasoning holds.
How it applies here: Addresses the people making the argument rather than the argument. Their manner is not evidence about the conclusion.
Drawing a general conclusion from a sample too small or too unrepresentative to support it.
How it applies here: Generalises from the most visible examples to everyone holding the position, when visibility is exactly what the sample is selected on.