Not everyone we dislike is a jerk. Sometimes all it takes is just that they are different. Sometimes they just don't coddle us. Sometimes they just don't give us the respect we *think* we are due.
Jerks are people who set out intentionally to hurt me or injure me. On or off the mat.
Let me make a rhetorical argument about another way to look at injury, harm, and compassion.
I missed out on the ki/kokyu skills in judo because all my instructors were westerners and there is a lack of knowledge of these skills, even among many of the Japanese, because the knowledge was kept hidden. So fair enough.
I missed out on these skills in Uechi Ryu karate because I wasn't smart enough to grasp the fact that some of the things I was shown (a couple of them privately) represented some form of movement I didn't know... I couldn't even conceive of such a thing, so the fault was my own. But I like to think that if I'd had the time and been able to train with a really well-qualified teacher (like I had), I would have been able to put the clues together.
There are a lot more clues about these skills available in Aikido than I ever had in karate. Heck, there's even videos of people like Ueshiba, Shioda, Tohei (I use those examples only because they're the ones I personally have viewed the most often), and others. Yet the thing that "injured" me the most in Aikido was that I spent 7-8 years without finding a teacher that could competently teach these skills.
In fact, I think that's the biggest "injury" that is inflicted on most Aikido students.... they spent many years and didn't get something this basic. Sure there are a lot of other happenings in a dojo setting, some good some bad some abusive some good, but the single biggest harm or injury, in terms of ultimate cost and in my opinion, is to get through many years of a ki/kokyu/qi/jin skills martial art and realize that a teacher or teachers didn't get the full (and basic) stuff to you.
Now would we say that most of the Aikido instructors are good and compassionate people? I think most of us would. But how about if I mentioned that a number of similar conversations about the ki/kokyu skills went on in the Aikido community 10-15 years ago and a lot of the then (and now) high-ranking yudansha simply blew the possibility of these skills off because they couldn't conceive of something (despite the vids and books) that they didn't know?
I'd argue that there are a lot of "compassionate" people can do great harm and injury, using that example. Nowadays there are a number of Aikidoists reading this forum, as an example, who don't know these skills. I'd ask why they don't know them.
A lot of times in a workshop, as the logic begins to develop and people get a grip on basic principles, I watch some of the senior people. And trust me I don't watch from any great godly height, because I've been there myself not too long ago. I watch those senior people to see what there reaction is to finding out something that they should have known long ago. Most sort of take it into stride, but it's a big pill to swallow. I've had some people tell me they'd just realized they wasted 20 years. A number of people simply quit the martial arts, some to work out on their own and some just quit everything and were a bit dejected.
My point is that "compassion" is a tricky thing. The nicest, most 'compassionate' guy in the world can injure you through neglect and/or self-absorption or not being smart enough to figure things out. Remember that it's common in traditional Asian arts to ask someone to be smart enough to "steal" a technique. The guys who can't steal the techniques fully are often the guys who go on to teach. Harm, injury, and compassion can be a difficult jumble to separate, IMO. So this topic of "would you show power to someone who is not compassionate" is tricky indeed.
Personally, I tend to think most people have selective compassion; I look for constant ethics and the intelligence/perseverance it takes more than I worry about compassion. You want a nice, compassionate guy to teach you Aikido? There are lots of nice guys out there and yet look at this ki/kokyu debacle.
My 2 cents.