If F.B.I. agents can't create Domestic Terrorists to arrest, then how come cops can create criminals?

So, I heard somewhere that F.B.I. agents could not create Domestic Terrorists to arrest. It was said by someone on the television (of course I was unable to get the respected person’s name) concerning the hearings on January 06, 2022. I am pretty sure I was tuned to the MSNBC channel.
With that said, I thought to myself, well, if FBI agents are not allowed to do so. Then how come cops can use their discretion (suspecting criminal activity) to start a rolling resume. Only to arrest you 20 minutes later, a mile from one’s home. Sounds to me as though he is creating a criminal. Especially, when he did not approach me after assuming criminal activity was going on. By the way, I was letting my engine cool down, and filling my radiator with water. I feel as though this officer was coming down off his adrenaline high. He needed a quick fix, and I crossed his path. I have other incidents like this, but that is for next time.