vegan

"skill issue"

IMO, people who experience health effects from cutting out flesh either failed at meal planning or they're sensitive little babies who couldn't handle a change. I empathize, western pattern diet depends on flesh and I guess it's jarring to make a big dietary change of any sort (though it wasn't for me), but that is what you're signing up for. Maybe ask about specific things, like "how did you get enough protein" or "did you take B12" and find obvious mistakes. Broader level though, animals still don't want to be killed even to give a carnist a better night's sleep.

Short of just having a bad veg diet

That's a pretty easy thing to do, yeah? Most people think of vegetarianism and they think of potato chips and salad.

Try asking them what they were using for protein and tell them to try next time.

I get really politely pedantic and start asking them how they know this, what the nature of their experimental protocol and controls are, if they made any effort to do blinded testing. If they're smart they realize how silly their refusal to openmindedly consider their conviction is based on false assumptions is and if not they get big mad and make sillier claims that tend to get progressively easier to deboonk

Honestly I guess those that suffer from chronic anemia and aren't able to do the whole combine leafy greens with vitamin c rich sources (to aid in iron absorption) alongside beans. Tbh though it requires likely having specific intestinal issues that make it hard for certain people with conditions like IBS, UC and FODMAP.

Kinda feels like they've been getting a little too much into Tokyo Ghoul.

Also, no veggies makes me feel less well.

Any change in diet will take time for your body and gut microbes to adjust to. Going suddenly from a lot of meat to zero meat may absolutely cause people to think that the vegan diet is unhealthy for them

Yes meat makes your health badder