I think they should. Not that Foley shouldn't have been able to keep his seat until there was a good investigation.
It is the fact that the leaders knew about these emails and kept him on the missing and exploited kids subcommittee.
An analogy: A cop shoots a bad guy. It doesn't matter if you know it was righteous, aren't sure, or you think it was a bad shoot. The guy gets desk duty until the investigation is over.
Leaving Foley on this committee is inexcusable and is horrific leadership. Anybody who knew, and didn't do anything does need to go. Foley is responsible for what he did, but the leadership is supposed to lead. They apparently didn't. If true, we need new leaders.
Weighing just the e-mails against his record on child advocacy issues I could see where this might not have been as painfully clear as it is today. If, as has been alleged, there was a general knowledge of Foley's inappropriate behavior then that is a different matter. And if there was a general knowledge there are a whole lot of people who seemed to have failed.