Cops fucking suck as a general rule, but guys, there's room for nuance.
I think at this point, any PD should have some training on issues like swatting, because it's become an epidemic recently. So far as I know, though, there is no "clearly established law" to that effect. It's possible the court interprets preexisting law about what police can do in response to 911 calls in general as establishing a duty of responsibility when answering a hoax call, but that sounds like an awful lot like expecting every officer to be a lawyer.
Hope v. Pelzer is the leading case on this kind of interpretation of "clearly established law." A District Court had thrown out a prisoner lawsuit alleging violation of civil rights by binding him on a "hitching post" in a stress position for some minor infraction. The court's reasoning was there was no "clearly established law" specifically addressing this form of torture.
Ultimately, the Supreme Court responded that it doesn't have to be exactly precise as to the details, but harsh physical punishment that amounted to torture is clearly established to be unconstitutional under the Eighth Amendment. You can't just wiggle around that by coming up with some novel method of physical torture.
So basically plaintiff's counsel is going to have to argue that some level of responsibility applies to responding to 911 responses in general and the police violated that and should have known it was a violation ("clearly established").
I don't really see that flying since Pat's essentially arguing they should have established a special protocol just for him to respond to a situation apparently relatively novel to the MPD.
That said, it's already (partly) survived a motion to dismiss, discovery is expensive, and 1983 lawsuits have a small but nonzero chance of a plaintiff's victory that gets a ridiculous jury verdict, so offering a lowball settlement to give the squealing pig a nominal victory is a definite possibility.
If it goes to discovery, and it seems to be headed there, the next opportunity for a bite at the apple on a qualified immunity argument is probably at the summary judgment stage, if Fatty doesn't somehow get in discovery shenanigans that lead to terminating sanctions. Presumably, his lawyer knows he has a client who needs some tard wrangling and may wrangle him into compliance.