I think the division Theravada/Mahayana is unneeded. I did watch some things, but found them incorrect so as a response I added some comment to his video. Those comment I really worded nice and kindly with good arguments if I say so myself, but he did not respond and actually deleted it. I don't say this to discredit him, but just to say why at the replies on his channel you may mainly find comments that agree with him, or perhaps some replies he could easily deal with instead of those that really pin down the problems of his approach. I say this so you know there are many more that agree with you and what Brian Ruhe says is just what Brian Ruhe says and is in no way representative of some general Theravadan view (which you rightly say is impossible anyway).
But as a general remark you more often see people trying to justify their own beliefs by criticizing others. Even on things like outer appearance, people are putting others down so they get more self esteem. Or people point to other's mistakes so they seem smarter. I think this is a really unskillful way to go about things and something you will see done by someone who isn't really sure about his own way of going about things. In the case of criticizing the way others practice, it to me points to a lack of results of ones own practice. So teachers who mainly seem to criticize others, especially in an unskillful manner, I would just ignore. The Buddha said some things along those lines in some suttas also: that one shouldn't say "I understand and you don't, I practice right and you don't". Don't know the exact sutta but I vaguely recall somewhere in MN10-20 ??