I'd say its the "I'm too old for this shit", attitude. If you want to get in early and leave early that's fine but If you don't put in extra hours, there will be decisions made when everyone else is in the office and you went home. Then you bitch and moan like its ageism but they're asking the team to conform to their hours and that's just not going to happen.
Plus there are plenty of people who have the "I've been doing it this way for XYZ." Don't tell me innovation stopped when you got the Sr. in your title. If you're coding in Java and refuse to type your collections, I hate you.
If you click with the team and have gray hair, I'll love to learn from you.