You can swear at police as long as you don't actually threaten harm to them.
Swearing at police and using profane, insulting or offense words that is directed towards police is not enough to get arrested or charged for disorderly conduct.
However if you actually makes threats to harm the police such as saying, I'm gonna shoot you or kill you or your family etc then you can and most likely will be arrested and charged with threats.
You can also flip a police officer off and you can't be arrested for that either.
But if you happen to swear around kids or in places where they have disorderly conduct laws in ordinances etc then you may get charged with disorderly conduct but not for simply swearing or cursing the police out.
You might get arrested by a police officer that wants to arrest you for swearing at them but they would likely have to drop the charges against you and let you go.
Just because a police officer arrests you for something it doesn't mean they actually performed a legal arrest.
And it also is not illegal to give a police officer the middle finger.
Although it may be considered rude or disrespectful, giving the police a middle finger is protected under the First Amendment right to freedom of speech.
Police officers cannot legally arrest or cite you for this gesture alone although some may try.