First, you don't use warrants, you use subpoenas for non-parties and discovery requests for parties.
Second, abuse of process is illegal and actionable. That's when a court process is used for a purpose other than its intended purpose. Whether the activity is an abuse of process or privileged litigation activity turns on many factors, his tweet does not help him.
Third, attorneys can also be liable for abuse of process, so he has to find one willing to take it on. If he can't, he can't issue a subpoena or discovery, only the court or an attorney can, so he has to get the court to issue each.
There's also motions to quash subpoenas. Just because someone requests something doesn't mean they get it. You can object to the subpoena via motion to quash. You can also just object in the response and make him file a motion to compel response. The grounds for objections and quashing are many. Discovery can be similarly limited or objected to.
Finally, he's being way dramatic and doesn't know the proper term. This is typically a sign that someone is full of shit and can be ignored.
Anyone who litigates self represented in anything other than small claims is a fool. Procedure alone with fuck them. Decorum and when to make argument will also.