Banner -- a former Eagles president and Browns CEO -- says he doesn't see how that's logical ... and tells TMZ Sports it's clear the 'Skins didn't want Kap because of his political beliefs.
"It clearly means the Redskins are blackballing Colin, and I think they're doing it for political reasons," Joe says.
"The team happens to be run by two guys that have been very clear in their politics in Bruce Allen and Dan Snyder, and it's clearly not a good political fit."
Joe says that's crazy to him as a former NFL personnel exec ... saying if he were a current player on the 'Skins -- he'd be pretty ticked off.
"I just don't see how you can look at your team, who's been working here since last July and use that as an explanation to not try to be the best you can be at the moment."
Banner added of Colin, "Yeah, he'll bring some media focus on the team and so on and so forth, but small price to pay, especially since you've already indicated for the right situation you're willing to pay it."
Banner -- who was part of the Eagles team that brought in Michael Vick after his prison sentence -- says if he were still in a front office, Kaep would have a job on his squad.
As for Foster ... Joe couldn't say the same -- telling us the allegations against the LB are just "too egregious."