[r-a-y]

is_feed() is what you’re looking for. However, I would use travel-junkie’s code as it’s cleaner:
https://buddypress.org/community/groups/how-to-and-troubleshooting/forum/topic/how-to-make-a-private-community/?topic_page=2&num=15#post-44616

Modify this line:
if( bp_is_register_page() || bp_is_activation_page() )

with:
if( bp_is_register_page() || bp_is_activation_page() || is_feed() )