It's funny but when you're talking about illogical people or people who are more lead by their emotions than logic any and everything can lead you to be called a douche bag. When it comes to a lot of people there doesn't need to be any actual backing when others are called things. They don't need proof. They don't need a reason. They can just call a person a thing and other people like them will automatically believe what they've said.
When it comes to more logical people or people who are more lead by logic that changes. People will be presented with why said person said it. And it will make sense why the person said it to others who also prioritize logic over emotions.
And sometimes that logical proof is already there for other logical people to find.
Generally speaking though. A douche bag is someone who mostly acts immature. Who may attack others based on nothing. It is though possible to be both immature and to attack people based on facts. Seeing as how douche bag just generally means an asshole it's not abnormal for a normally chilled person to act like a douche bag for valid reasons.
Again though, the differences there is the presence of or the absents of logic. To whatever degree.
And as
Hatt_101 said. Men, women and trans people can in fact be douche bags.
(Also can a douchebag not have an ego and can an egotistic man not be a douchbag.)
Everyone has an ego. The difference is whether they're being logical or how much more or less they're being logical than blank. Someone being egotistical will always be a douche bag. Since they will always or in any given instance prioritize their ego over everything and everyone else. Again though, it doesn't automatically mean that's a bad thing. If given they are being logical or more logical about a given topic. Even an egotistical douche bag and can be right about something. Just like a broken clock.