There's an interesting point that Alan Watts brought up about dogmatism in nondual teaching - which is that the REAL point is to MAKE you rebel and finally realise these teachers don't know better than you do. That can be a technique to help you wake up. Give you a bunch of silly rules to follow, until you eventually stand up for yourself and say "no I don't need this, I am enough".

Of course most gurus don't do this with the intention of causing you to wake up by rebelling. Most of them would be horrified if you did. That's a sign of a cult. Ideally a guru would applaud if you rebelled against them and say "well done you finally got it!"

As for "not being flawed and human" - even Alan Watts was a flawed man who was an alcoholic (and died early as a result). Yes he shared a lot of wisdom, but he was always open about the fact that he was a flawed person and always would be. And in fact you should never trust anyone who claims to be perfect.

The whole "In group, outgroup" thing is a HUGE red flag too. After all, if enlightenment is realising that separation is an illusion, the fact these supposedly enlightened people think they are "better" is a sign they really don't get it at all.