That does come off,although there really is no need to is things are not rusty.It is not part of a seal,it IS the seal.No rubber involved.More of a dirt shield.
It does come off, plastic door wedges used by carpenters will bring it off without scaring the spindle. I found that a short length of ABS pipe was perfect for driving on a new one back on.
As noted, it does come off. With that said, the spindle looks like at least one bearing has spun on it so it would be good to confirm whether it's usable as is.