Isn't there a SYNC option in System Preferences then? I'm not at my Mac to verify this but I'm positive there's a SYNC icon, then the option to remove the Sync icon in the menu bar should be there.
Regardless if it's there under .Mac or under Sync, it can be removed via some options.
Sync is not exclusive to .Mac, since I DO have .Mac that's where I see the option to remove it from menu bar which is why I posted it and also the OP's title said .Mac which is why that was the first place I looked to verify the option was there.
And to further clarify the OP did not say whether he does or does not have .Mac account.