i feel it totally depends on the context.
personally, this is my opinion:
multiplayer:
non-intrusive cosmetic glitches like weird costumes in fighting games: okay.
intrusive cosmetic glitches like outlines trough walls in a shooter: not okay.
actual gameplay changing glitches like skipping half the course on racing games: BURN THE WITCH!!
singleplayer: everything is okay, unless the playthrough was intended in a competitive fashion, like a speedrun or a race.