It's not a cop out. That's how debate works. You take a position, it's on you to prove it, not on other people to prove the opposite or accept your position. Prove your case or shut the fuck up. And repeating the same baseless assertions over and over is not providing evidence. You want to argue the team is bad at base running, provide actual data (not just anecdotes) to that effect.
You want to argue he's bad at bullpen management, dig up stats to support it (again, not just anecdotes).
Hell, you want to argue he's just a shitty manager, bring something, anything other than "that one time..." or "they clearly can't get better with him at the helm" with no data to support it.
Again, it's on you to prove your case, not to insist someone else prove the antithesis or admit you are correct.
But just for the sake of making you shut the fuck up, I think Farrell makes this team better than the average manager, and would even argue he's likely a good manager. Here's a link to back it up:
https://www.fangraphs.com/blogs/how-should-we-evaluate-a-manager/
I don't agree with the conclusion that Farrell is among the very best, but there is some pretty compelling data in there and frankly, I don't see you one could read that and come away with the belief that he's a bad manager.