I've seen, in many a honbasho:
long extended niramiai,
a lot of rikishi NOT bowing after the match.
I have NEVER seen trash talk outside the dohyo, post bout. That was weird but no punches were thrown, at least. Both of them should be reprimanded.
In July 1987 (you can look it up), Konishiki shoving a fellow ozeki after defeating him in a match. Just an extra shove just after the match was over. I don't recall anyone being scolded.
As for Roho's locker room tirade, that's different. Sure doesn't show gaijin rikishi in a good light. His old shisho, Taiho (one of sumo's ALL-time great yokozuna) should come out and kick his ass.