I mean, it's sexual assault obviously, but in this case, "using a sex toy on them" provides a bit more context than just generically labeling it as "sexual assault". Sexual assault could be many different things.

The article also goes on to describe that they put the sex toys in the men's mouth. I think the "used a sex toy on them" is just more descriptive in this situation, because if they used "sexual assault", people would not be able to decipher what these POS officers actually did.

I do agree that the media can be terrible about minimizing sexual assault on men, but in this case I think the headline is more descriptive. Also , fuck these racist rapist cops.