Is Mahasi Sayadaw's "counterfeit dhamma"?

There are certain people on this website and one in particular who claim to know the only "true" teachings of Buddha and they are saying that following Mahasi Sayadaws and other masters teachings where you focus on the movement of the breath at the abdomen is not what Buddha taught so therefore it's incorrect practice and "counterfeit dhamma" and will therefore not lead to enlightenment. I absolutely do not agree with this. It reminds me of fundamentalist/evangelist Christians who take the bible literally and follow the Old Testament etc and tell everyone they are going to hell for not conforming. It's actually disappointing to see people behaving like this around Buddhism but I suppose at the end of the day it is just another religion so it's to be expected that dogma and zealotry will be part of it. What do others think?