I have 2 alts I've taken through Ultima Weapon. Worse incident I saw was a tank blowing up at the astrologian who was just trying to learn their job in Stone Vigil, but I've seen it in Brayflox with the add pulls too. No commentary about how to improve, why they should be aoe-ing, how they need to check their new abilities or *shudder* equip their job crystal. Just Vitriol and kick.
Is it the majority? No, of course not. Ff14 wouldn't be known for its friendly community if it was. The op wanted to leave parse shaming out of low content, and I'd agree that 15-45 is good room to allow growth without explosive harassing. I'm not saying ban fflogs, or parsing. I enjoy it myself for improving. I'm saying leave it out of the low low content