My guess is that SE's management isn't really thinking things through and/or properly listening to the CMs, yet again.
Maintaining an open platform while trying to prevent something that a substantial minority of the engaged user base wants to do is going to be difficult and require significant work from the already over-stretched CM team. Plus the campaign will get another publicity/funding boost just from this.
The best legal advice balances legal risk against other issues like reputational risk, practicality, business risk etc. It doesn't sound like that's happening here, either with the decision to clam up after defaming Monica, or this latest action.
EDIT: Cesar M's comment clarifies that there won't be a bulk exercise to find and remove these links, they'll just be removed if employees happen to find them in normal use of the site. That sort of makes sense in that it means SE aren't knowingly supporting the campaign, even if there may be plenty of the links they haven't seen.