There's a guy pretty much stalking my friends on facebook and they wont listen to me!!?

im very cautious about who i add on facebook. I will only add someone if im POSITIVE i know them. I added this person a while ago but deleted and blocked him when he started posting perverted comments on my profile. He now is friends with all of my girl friends and does the same thing to them. Im starting to get really freaked out because they will post statuses like "going to the _____ mall tomorrow" and he'll comment saying "the ______ mall in _________?" and theyll say something like "yeah where else?" so not only does he know where we live but he has access to our last names which you can just google to find information about anyone. Ill tell them to delete him because they obviously dont know him and he is much older than us not to mention his profile picture is a picture of a guy looking like he's in his mid 20's but they wont block/delete him. im getting scared for my friends' safety... and mine.