I recently added to the common arguments section on my site.
There are tonnnnnns! of 'hasty generalizations' (the name of the fallacy) made about vegans, the most prevalent being that our food tastes awful (because someone had a sloppy, soggy piece of tofu one time) or that we are all unhealthy, because someone knows someone who knows someone who claims they know a pale non-energetic vegan, or they've talked to one of the ex-vegans who now know everything about nutrition and have become paleo or something like that.
The point is that one must collect ample data before making a generalization. And, I am afraid that a sample of 2 or 5 or a dozen does not create an even slightly meaningful sample in this case, especially if there are not the restrictions and controls in place, that one might find in a scientific or in this case social scientific study.
Go check it out!