Easy to call someone a coward from this side of the TV screen. I know you don't really mean that, though.
No, obviously I don't believe Tibau is a legitimate coward. I'm not some schmuck like Roflcopter who calls out fighters for ducking, etc. But Tibau has relied on size as opposed to actual skill for years now. I suspect he'd not even be an average WW, which is why he cuts to LW in the hopes that he might be able to outmuscle his opponents. It's the same thing Anthony Johnson did, and people crucified him. Yet Tibau always manages to get a pass. It's time for him to move up to WW.