These are politicians making political judgments about Franken, not necessarily moral ones [View all]
...and dirt-dumb political strategy, at that.
'Zero-tolerance' is being used here as a slogan, not a responsible policy which will judge accusations on merit and degree. There needs to be some system in place in which there are clear, defined guidelines for behavior and consequences which are mindful of the degree of the offenses or allegations.
Moreover, there needs to be more than just some semblance of due process, especially when making judgments about anonymous or unsubstantiated accusations. Due process isn't some dodge, it's an integral function of our system of justice.
Then there's still the matter of the precedent set for this forced resignation from Franken's own party members rushing to protect their political selves without regard to the almost certain exploitation by republicans of some Democratic pols' reflexive need to self-immolate, and their timidity in demanding accountability from their republican counterparts.
This isn't a 'line drawn in the sand' as some have mused, unless it's applied to more than just our own party, and unless it's applied with fairness, based on clear evidence of actual harm to someone, not just a bruise on a party's political profile.