Sybil attacks
1. can refuse to relay transactions and slow down block propagation to other nodes.
True, but trivial to counteract.
2. can isolate your node from the network and block you from syncing with the network.
True, but trivial to counteract.
3. can in some rare cases cause you to run on a temporary fork.
True, but trivial to counteract. As you point out. Though 'trusted' is not really as important is avoiding nefarious peers.