This is a terrible argument:

• it affirms the consequent;
• the assumption that all social activity reduces to fitness strategies is in sharp contrast with reality and lacks evidence;
• even allowing for the unreasonable assumption and overlooking the fallacy, the problem remains that apart from some anecdotal evidence, nobody has a clue as to whether PUA works, including people who denounce it. The most that could be concluded, even under the manifestly unreasonable assumptions, is that people who denounce PUA believe that it works, or have anecdotal evidence that it works. However, since it's reasonably common for people to both denounce PUA and believe that it's practiced by pathetic unsuccessful creeps, this conclusion is wrong, too.