I'm going to get down voted for saying this, but you are 100% correct.

Sure, it is her choice to use her body as she wishes, but as a father it is your job to explain her that choices have consequences. May be rather than having an argument, have a proper chat with her. Sit her down and explain your concerns and the part of "choices have consequences". That's what a lot of young women don't realise these days and they think their choice will not affect their life in the future.

It may be in her best interest that she doesn't cut herself off from you completely. Obviously, she hasn't made a smart choice and needs you (her father who genuinely cares for her) more than ever. You need to be smart here in guiding her out from that platform. So in summary, you are not being the asshole here, but don't isolate your daughter - that will have worse consequences.