If they don't call on Franken to resign, too, that would be a valid card to pull. If we don't call for Trump to resign as well, it would be valid to call we on the right of center hypocrites.
Franken, Conyers, and Trump deserve proper investigations and deserve the right to be assumed innocent until proven guilty - all of them, or none of them. If accusations are all that are needed to cause realistic calls for resignation, we should all be shouting from the rooftops to have Franken, Conyers, and Trump resign. If they're not, we should all be shouting from the rooftops to have them all investigated, and let the chips fall where they may.
Now, this could be court, ethics committees, and/or impeachment processes. They were all elected (well, not Franken, but you know....), and they all deserve the same treatment from us.