Hey OP,
Firstly, if there is a thread about veganism on MN, people are only going to post if they have relatively strong views on it. If you are not vegan, the main reason for posting would be be that you object to veganism. So you are automatically excluding the vast majority of MNetters who have no view either way.
I think it is a vicious cycle. Omnivores feel vegans judge them and vegans feel omnivores judge them. Both parties defend themselves and both parties come away feeling their view of the other as unreasonable is justified.
Food is part of our culture and heritage. It carries a lot of emotional weight. Certain foods hold memories and emotion for us. For someone to stomp all over that by saying the food our parents and grandparents fed us and what we make for our children is bad is insensitive and unlikely to get anything but hostility in return.
I would much rather see a thread where vegans share lists of easy vegan alternatives, which foods people eat every day are actually vegan and making veganism more accessible and inclusive. The world is not going to be saved by small numbers of people going vegan, but by encouraging everyone to reduce their meat and dairy intake.
I am vegan and I know it can be daunting for people to make food for me. Because people who cook for me are my friends, I make it as easy as possible for them by bringing stuff or talking through what they planned to cook.
One thing I do hate is the idea that raising children vegan is bad for them. Vegan children can be very healthy and very unhealthy, just like omnivorous children. Vegan parents are aware there is a risk of deficiency so they are likely to check things and use supplements. We love our children as much as the next parent and want them to be healthy.
FWIW, my kids aren't vegan or even vegetarian. I make a lot of vegan meals but they eat school dinners and are allowed to try whatever they like. There is cheese and milk in the fridge and they have both dairy and alternative yoghurts. I don't guilt them or try and frighten them with stories about animal welfare.
Most of my vegan and vegetarian friends have similar attitudes. I have met 1 asshole vegan and it is because she is an asshole, not because she is vegan.
Apologies for how long that was 