I don't know if I would really describe him as an asshole, honestly. He wasn't going out of his way to be abrasive, he just wasn't what the Main Character crew were used to.
Sure he was too rigid and uncompromising for Enterprise, but on literally any other vessel he'd be pretty standard and quite effective. We often forget, but for all intents and purposes Starfleet is a military, and as far as military commanders go he really isn't that bad.
Sometimes the crew has to adapt to the captain and not the other way around, especially in the short term. Picard was way too fucking lax sometimes.
The example I always point to (and I just rewatched, along with all of TNG), his plan with the Cardies was unnecessarily stupid.
1. Reassign a big chunk of his engineers to security.
2. Make a ton of arbitrary changes to the ship and give the (now severely understaffed) engineering team minamal time to carry them out.
3. Only ever allow 3 Cardies at a time onto the ship. (Smart) but what was all the extra security for? If it was *absolutely* necessary, couldn't you at least let the nerds do their jobs first and *then* give them guns?
4. (this one is the worst) Not tell *anyone* what his actual plan was. I get making the Cardies wait around for him to show that he's the Alpha dog or whatever, but he didn't even tell his own crew what he was doing, and then he proceeded to fuck around for an hour or so in his ready room, without even telling Troi *what* he was doing, or what he expected her to do. There was no benefit to this, she wasn't even questioning him, she was just rightfully confused.
Imagine what would have happened if Troi had misunderstood and sent the Cardies into his ready room to meet him. (At least he made it a specified priority to get the fucking fish out of there >. >)
He wasn't. Riker was the asshole for being insubordinate.
Riker literally did his job, and as the show says he should multiple times, he did so in a way that didn't undermine the captain in front of the crew. (unless you count Troi, which I don't) Riker was a bit smarmy when Jellico came crawling back to him, but I think most people would be at that point.