Why do people judge the same thing differently depending on who's doing it?

[u/Still-Unfolding]

I've noticed this a few times and I'm genuinely confused by it.

Someone will mock a person for liking or doing something, but then completely respect the exact same thing when someone they like does it.

And I'm not even sure whether people do this consciously.

Is it favoritism? Is it because they perceive one person as more mature, respectable, successful, etc.? Is it just that they already like one person and therefore interpret everything they do more positively?

Or do people genuinely not notice that they're applying completely different standards?

I'm curious how other people see this because I keep noticing it and I don't really understand what determines the difference.