If I give anyone information I ask them not to put it up on Ancestry or Genes or any other online sites.
Mainly because of all the junk trees and rubbish connections on there. This means I do not have many online contacts, but as I want to prove EVERY link myself then that is fine for me.
Others love putting their trees online. Fair enough. But if they have definitely put YOUR data online in an unsourced way, (as is most of the rubbish on Ancestry), then you should ask the person to remove it, and then ask Ancestry.
BUT if you did not tell the person NOT to put data from you online, I think you have a much weaker case.