Blanket "hide this activity"

Currently, whenever we approve a new member to join our group, there's a notice of the activity on the main page. Since we often approve dozens of new members at the same time, the first three or four pages of our Recent Activity feed are all "so and so joined the group." This makes it hard for visitors to look over recent discussion topics since they have to click through so many screens of "so and so joined the group." Is there a way to set up some kind of blanket rule so that whenever we approve a new member it doesn't show up in the Recent Activity feed? 

I know I can just go through one by one and click "hide this activity," but that's pretty time consuming when I have to do it for a few dozen people at a time.