For evidence, you'd probably produce screenshots of their profile and threaten to send them to people who know the blackmail victim. Now maybe having the Grindr logo on there is a bit scarier, but any other dating site with a profile listing "taboo" interests should work just as well.

Regarding your edit: I didn't mean that there was another Chinese company owning a dating site used by Westerners, but that it would explain what made Grindr special if there weren't another such company.