" I was just asking to do some mind gym here, question common beliefs. But I know that people dont cope well with this sort of thing, they are way more willing to not question. "
Ahh, so it's all our fault for not being able to perform in your mind gym.
I've been pescatarian for 30 years, since childhood, so it's not the first time I've encountered your wonderfully innovative argument, OP. Generally I'm puzzled by the way in which people will respect religious strictures ("I'm not eating it because a text written several millennia ago told me not to") but dislike the arguments put forwards by vegetarians ("I don't want to eat animal flesh, farming methods are cruel, they're a poor use of the planet's limited resources").
As far as reciprocation goes, you cook a meal the vegetarian can eat, the vegetarian cooks a meal you can eat. Errm, that's it. I think part of the problem, as illustrated on this thread, is that some people think that vegetarianism is about eating limp omelettes, or constructing a meat-based meal and then using a meat substitute. Good vegetarian cookery is far from this. Vegetarian cooks can have a wonderful understanding of flavours and produce exquisite and filling meals. Vegetarian cookery really doesn't have to rely on Quorn, or fake-sausage rolls. I usually find that by the time I've given guests 4 courses, including a chocolate orange cheesecake to die for, they're not hankering after meat.
If meat-eating friends or relatives are staying with me for several days, we reach a compromise. This is easy for me as I do eat fish (carefully sourced) but there are other ways around this. I don't like people cooking meat in my kitchen but I tolerate them getting meat-based sandwich fillings for lunch or putting meat toppings on pizza. I don't like it, but I turn a blind eye to bacon cooking in the morning as well. Or, we'll just go out for a meal.