Perhaps they shouldn't be, but as a practical matter, it would be disastrous for the Hall to allow folks already inducted to be booted out, at least absent a criminal conviction for something like fixing games. Creating after the fact standards for playing quality or known behavoir would make the honorees question the honor. That would weaken the Hall's bonds with a key constituency: the honorees themselves. Honorees attract folks to the Hall, especially at induction time, and they provide much of the memorabilia on display. It's already difficult to get such memorabilia when there's real dollars attached to this stuff today, and it would only get harder if a after the fact standard would be allowed. It's a potentially disastrous move, with very little counterbalancing positives from the Hall's perspective. I don't think the Hall's management is that stupid, especially when doing the stupid thing runs counter to another cherished Hall tradition: hew to the status quo! The Hall loves nothing so much as "tradition", and certainly what you ropose is not "traditonal".
Seen on a bumper sticker: If only closed minds came with closed mouths.
Some minds are like concrete--thoroughly mixed up and permanently set.