I feel that sympathy isn't really required. The bartender, by numerous accounts, was a dick. That doesn't mean he wasn't cared about by someone, somewhere. The bartender could possibly have been a nice guy once you got to know him but based on first impressions, he just doesn't want shit happening in his tavern due to a good business sense. No free room for the bard. No animals inside the tavern. Makes sense. NPCs can give off multiple impressions to different people, because that's just like real people meeting. 

It really boils down to how your character would feel. Aldred is a good example of the 'good guy' who despite briefly knowing the bartender to be a dick, is willing to look past that for the sake of Emilia. That makes sense because that's how I feel Heat wants his character to be. But your character can do whatever they want. You can talk ill of him if you want and feel like that's what your character would do.