person 2:caues me and that bitch in a facebook beef
person 1:y'all petty as fuck
If they BLOCK you after you friend them, that would mean they have a definite, very strong Facebook beef with you -- and thus a beef in real life too, that they aren't telling you about.
There are three grades of Facebook beefs:
Code Yellow: They hit reject, but not twice, so you see the "Friend Request Sent" button grayed out when you visit their profile.
Code Orange: The "Add As Friend" button re-appears, meaning they definitely don't want to be your friend.
Code Red: They actually Block you and their profile disappears into the cyber-void. Only for very grave offenses, at least in the Blocker's mind, and which the recipient of the Block may not even be aware of.
CAVEAT: This definition is primarily meant for platonic same-sex relationships (guy-guy or girl-girl, assuming all parties are straight). Guy-girl interactions are more complicated. Also, it doesn't count as a beef if the other person is a mere acquaintance and not in your peer group; you might simply not satisfy their criteria in accepting you as a friend. That said, if you have over 50 mutual friends and/or share the same peer group, and do know them personally, and they still reject you, it's probably a beef.
Person C: Looks like B has a Facebook beef with you.
Person D: What? E actually blocked me! I can't find his profile anymore!
Person F: That sounds like a REAL Facebook beef.