The colloquial use of "karma" is the idea that what goes around comes around, which strikes me as a very very good way to victim-blame. In fact, that was basically its function in Hinduism where it first arose. It was a way of saying that slaves are slaves because they deserve it, as suffering is always caused by the person experiencing it and not any external injustice. In fact, the idea of karma doesn't seem to allow for the idea of injustice at all. I've seen far too much of that in my short years alive to subscribe to a system which doesn't include it in the overall picture of reality presented. Therefore I would be a bad Hindu, and am kind of averse to it in Buddhism as well. I've heard different explanations from Buddhists of the Buddhist angle on the notion, but no one seems better supported than any of the others, and it just requires too much mental gymnastics to hold it in my head in some kind of painfully-specific way that doesn't feed victim-blaming tendencies in myself or others. Considering that the belief doesn't really add anything to my practice, nor would it change how I behave, I just... have sort of tossed it as one of the few elements of Buddhist dogma which can cause harm (since if it isn't necessary, and can cause harm, I see no reason why I should spend a lot of time building anything around it).