For several governments and agencies to be against mixers they bring some level of privacy to Bitcoin, it is an indication that they will see privacy coins as a big threat to their power.
They are not just against mixer but they are against any technology that will give us privacy and they will do whatever it takes to make sure that they deprive us from our privacy. We can see how they have bought some mining pool over to be on their side so that they can control which transaction should be added to the mining pool or not. And as humans due to greed, they forgot that it is only us that can make bitcoin more private by protecting bitcoin from the government. Monero has a better privacy than bitcoin because nobody cares about it, but everyone is after bitcoin for their own selfish reason.