I think the most difficult part is ... when the rudeness happens while the guest speaker is giving the presentation and speaking. A guest speaker is likely to not bring attention to the offending members.
Maybe that would be the perfect time for the guild president to stroll up and down the aisles putting her finger to her lips to show 'quiet please' and to pause and quietly ask offending members to quit their chatter.
These issues should be addressed at beginning of meetings and put in all guild newsletters. It seems some people are like children and need to be reminded over and over again.