The following will offend everyone who reads it. If anything you read below can be interpreted one way as profoundly offensive and in another as a mildly offensive joke, it is intended as the latter.
The preposterous dogma that all arts are effective in fighting. Along with that, instructors who lead people on to believe that by training with them, they will substantively enhance their self-defense ability (other than the fitness that they would just as well pick up in ballroom dancing or volleyball) when in fact they do not teach skills in fear management, verbal defusion of conflict, effective countertactics against edged and impact weapons, firearms, and multiple attackers, cement-friendly groundfighting, etc.
Ironic punishment department: I move that these instructors be taken into alleys and beaten by loud drunks in gorilla masks with sticks. The beatings will be taped, the tapes sold, and the proceeds will go toward rehabilitating the students they have deceived.
People who expect differential treatment on the basis of seniority, e.g. that junior students will address them using a special term. Get over yourself: you're in North America and this is the 21st century. I actually saw one guy say that because (the guy standing next to him) was his junior ("si dai") he could do anything he wanted to him. Then he smacked him in the face. (lightly, as a joke) That's an extreme case, but any time that ppl expect that their seniority confers some special entitlement, it's the same thing--different in degree, not in kind.
Schools that claim that weapons, sparring, etc. have to be done only after years of "foundation training". Gee, I wonder why the Filipinos never figured this out.
Self-defense instructors who brag about how many fights they've been in. That's a lot like a defensive driving instructor who brags about how many collisions he's been in.
Trappings such as uniforms, terminology and ritual when they serve less to contribute to safe and quality training or to elucidate concepts, than they do to support an image of oneself as a "martial arts badass" that one wants to have.
line drills and other dead patterns
Anyway, what's wrong with a system in which all frills (e.g. forms) are removed in order to distill true combat skills?