Partially, it's just the creepiness factor of otherworldly powers. Whatever the ethics of throwing a punch, I'd much rather be around someone who throws punches than someone who can boil blood and incinerate things with her mind. At least a punch is something familiar and understandable from which I know how to run away.Compare that with B'Elanna deliberately breaking Carey's nose, almost killing him. Is B'Elanna considered a bad person with bad behavior because of that? No! But Kes can be dissected, analyzed and nitpicked.
Tanis tempted Kes to burn the flowers in the Hydroponics Bay. Was it Kes's fault? No, it was Tanis's fault
Of course, one could argue that Star Trek is a show all about exploring the unfamiliar and learning not to fear things we don't understand. Yet, for all that philosophy, beings with extraordinary mental powers in Star Trek are typically presented as dark and creepy threats. "Return to Tomorrow" is an interesting case, because Kirk makes this impassioned speech about trusting the noncorporeal aliens who want to play with the crew's minds. He rhetorically connects uncanny mental powers with the ethos of exploration. But the noncorporeal aliens (at least one of them) turn out to be a threat, and in retrospect, Kirk's eloquent speech comes off rather naive.
I suppose "The Gift" might be Voyager's best example of a story that connected the value of exploring to the development of mental powers. Than "Fury" undid all the work done in "The Gift."