Yeah I often see this kind of vague posting about cancel culture, but generally speaking people are being cancelled (which can either just mean being criticised, or the more legitimate problem of people contacting employers) for either directly saying things that are offensive (the aforementioned -isms) or are implications that directly lead to -ist conclusions. My understanding is that the underlying complaint is that the social left has cultural power right now - conservatives are equally likely to "cancel" people for atheism or being gay or having an abortion, but when they are on the back foot use the free speech argument as a wedge against the same behaviour from the other side.