But they will die to them when a certain damage check is not passed in the future.
To OP: It sounds like you met one of the few impatient people. Usually the mindset is having people join mid-countdown, but I've seen the same types do so on a pug of a 1 run UQ.
If they are joining a lower level UQ, then yeah they really don't have business starting early. Such is just a meme outside of one scenario I can think of, and there are triggers for that.
If it us UH/Ultra Hard difficulty though, levels aren't in the equation anymore. Just gear and skill trees. Someone bragging about damage is often actually in the middle or upper middle of the damage ranges, from what I've met. The actually impressive people just do the damage.
In the case of berating for low damage though, it kinda depends on how low and the difficulty. A lot of our final content expects players to really bring in at least decent firepower.
There really shouldn't be any kind of reaction though outside of the very obvious signs of lacking damage.
If someone is fighting with any of the gold/silver 15 star folder weapons or any of the usual Zig 15 stars, it usually is as simple as a skill tree tweak or learning their class. Such shouldn't mean much in most content. Just give a tip or some info, point them in the right direction and its all good.
But if someone is entering with 9 or 10 star trash weapons or using any of the infamous "hit rapidly but do no actual damage" tactics, those tend to be more common ways of setting people off.
In a UQ with a damage check on UH, it can be a sign of an incoming failed damage check to anyone with a good eye.