You're an unregulated, unsupervised, and frankly unknown factor with no real accountability through any realistic chain of command to the results of the democratic process. However far from your imagined ideal, cops are.
Then the cops then decide to stop by his house to talk about it... that's intimidation and bullying by someone with a gun and the force of the government behind them.
Stalking, harrassment, and intimidation are illegal for you. Police can carry out these activities legally, by other names, in a controlled fashion, according to their duties and orders.
But if your tracking and recording of cops begins to verge into those categories, woe betide you going up against a judge who will find that you're interfering with law enforcement activities. Exercising your right to swing fists? That ends at the tip of the other guy's nose, remember?
They will let you, and you'll get away with plenty of it; but there's a line in the sand for you, and you stay behind it.
The same is at least less true for private citizens that are not being accused of a crime.