That's my point, you don't and can't. You should be cognizant of the possibility of abuse, not write off the possibility. Don't pretend to know when you couldn't possibly know. People who claim that abuse doesn't exist on Onlyfans are almost certainly wrong. How much abuse content exists on OF is unknown; unknown to everybody in this conversation, and unknown even to OF. Whether OF is ethical depends on how much abusive content is on OF, which none of us know, and how much abuse somebody thinks should be tolerated, which is subjective.
Anybody who claims that Onlyfans is ethical is making a claim about the rate of abuse which they can't back up.
Note that I am not claiming Onlyfans is unethical. I don't know if Onlyfans is ethical or not. I don't know what the rate of abuse content on Onlyfans is. That's information I simply don't have. Furthermore, I'm not even sure what rate of abuse content society should tolerate from a company. Probably if these are only isolated incidents that are swiftly recognized and rectified, it shouldn't damn the whole platform. Also, I think it probably matters whether that rate is trending up or down, but I don't have any information about either possible trend. I lack the information I need to support the claim that Onlyfans is ethical, and I think the rest of you do as well.