Worded as such it does appear threatening. If someone tweeted that about me I would feel worried about my personal safety and that of my family. The law specifically states that placing a reasonable person in fear for their safety via online communications is a crime.
If you're going to request personal information for a legitimate reason then you should word it in a non threatening manner.
"...it's also a request to identify a police officer, which has legitimate purposes."
And given the context of calling a police officer a "bitch", do you think the requester was doing so to accurately file a complaint... or doing so in the hope that armed with the cop's identity, somebody would engage in harassment of that man and/or his family?
Being charged with a felony for the tweet is absurd.
But painting this as an innocent request for information is almost equally so.
If you're going to request personal information for a legitimate reason then you should word it in a non threatening manner.