I experienced something similar in a totally different art, but yes, it can destroy the spirit of the dojo and risk injury to others. The 1st question i'd ask back at you is: if most of the students don't like them or their attitude, why the hell hasn't the sensei of sempai had it out with them or even cautioned or banned them? The wellbeing of the students lies ultimately with the sensei, so he/she should step in and sort it. Failing that, tsuki the living hell out of the b*stards, and see how they take it. Failing that, let the other guy confiscate his knees in the parking lot for him. I respect harmony in the dojo above all, but if these two tossers won't respect any of it, then deliver them the beating of their lives. Are they bigger and more menacing than the rest of you? Maybe a misguide kote to the knuckles will make a start...... good luck.