There's also the escalation timeline. In a hypothetical situation where nonlethal force is being used, but there's a threat that requires more than a gentle "please don't" type of heating, I don't think we'd want it to be limited. Gentle crowd suppression is great till someone pulls out a gun or knife, and though it's debatable opinion and there are a lot of factors to consider, I think a few collateral 2nd degree burns beats switching to a rifle and opening fire into the crowd.
LEO will use it against anyone they wish to. Why do people want a group that already has special privileges to murder you scot-free to have more powers? Anyone sane would be working to equalize matters by either kicking cops down to the same laws as us or arming up to the level as cops and arguing for the same immunities to murdering cos.
Take a look at the videos of police encounters posted online. The situation you're describing is highly theoretical. What actually happens is that you get pain compliance used to control talk back and disrespect of cop.
Will taking the tools of torture away from cops increase risks they face? Maybe. But have they earned our confidence that they will use these tools wisely? No, they haven't.