Maybe. I've seen a couple of Juve games between Juve fans. I've seen Bologna-Juventus and Fiorentina-Juventus between the home team fans. Neither fanbase is particularly annoying. It's mostly the generic anti-Juve stuff.
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Because it makes no sense pretending to be friends when you're anything but and the only 'benefit' either party is receiving from FB at this point is watching the other go on with his/her life or at least pretending to do so.