This isn't entirely true. Grindr is contractually bound by its privacy policy and that policy would not permit it to sell or disclose an individual's data, except as expressly provided in the policy. And that policy wouldn't permit this type of data sale, and wouldn't disclose data to the government without a subpoena. Thus, any individuals whose data was disclosed in violation of the policy has a legal cause of action against Grindr. However, it would have to be their personally identifiable data - I'm not sure exactly what was sold. It would not violate the policy to sell certain types of meta-data, for example.
Here's what the current privacy policy says: " We may access, preserve and disclose Personal Information to investigate, prevent, or take action in connection with: (i) enforcement of the Grindr Terms and Conditions of Service; (ii) claims that any content or behavior violates our policies or the rights of third-parties; (iii) requests for customer service; (iv) technical issues; (v) protecting the rights, property or personal safety of Grindr, its users or the public; (vi) lawful legal requests including subpoenas, warrants, or court orders or in connection with any legal process; (vii) establishing or exercising our legal rights or defending against legal claims; (viii) tax and accounting purposes; or (ix) as otherwise required by law, collectively 'Legal Obligations'."