And what exactly have they done to harm bitcoin?
Maybe, made everything to make transaction fees higher?
I didn't check it myself (I agree with that), but I've heard that there is quite a load of scammy transactions hitting the blockchain nowadays. I don't know and thus I don't claim that it is the miners themselves who are behind that but they certainly profit by that. Also, read at least the topic title. Why would they want to do that if not to create artificial shortage of transaction confirmation capacities, which makes people set higher fees if they want their transactions confirmed fast or just in a timely manner. It is not that any individual miner which is evil, it is mining monopoly which is, i.e. centralization of mining in a couple (well, dozen) of hands