I think that it would help if more vegetarian advocates focused on finding ways that non-meat diets can fit with people's lifestyles and preferences. For example, I don't like the taste of many vegan dishes and (back when I was more series about working out) I was looking for a high protein, high calorie diet. When I looked into veganism, a lot of the resources came across as dismissive of my goals or felt like they came from a perspective of "we're morally right so we don't have to find a way to work with people's preferences".
I'm not trying to say that's what the people giving advice actually thought; I'm just saying that's how I felt that it came across sometimes.
Totally understand your point, and the veg lifestyle is becoming much more mainstream in athletics. e.g. check out Nimai Delgado's (IFBB bodybuilder) instagram posts on simple, high protein, high calorie foods for bodybuilding: https://www.instagram.com/veganbodybuildingfood
I'm not trying to say that's what the people giving advice actually thought; I'm just saying that's how I felt that it came across sometimes.