I can't help but notice an aura of certainty in the facts the writer supports in his thesis.

I just can't see how a multitonne predator like T.rex could sustain itself by being an obligate scavenger. An average Tyrannosaurus would need many pounds of meat daily just to keep going and not engaging in any form of active hunting would have make it almost impossible to survive.

You don't have to be fast to catch a prey. You just need to be faster than it; or if not, you could have more stamina. Don't forget that most advanced theropods had respiratory systems similar to those of birds, allowing them to have the quick metabolism necessary for an active predatory lifestyle. In contrast, ornithischian dinosaurs, such as Triceratops and Edmontosaurus (likely prey for tyrannosaurs) lacked such respiratory mechanisms, making them less durable in a possible chase. There is fossil evidence to support the theory that T.rex was a predator and it only makes sense to be.

As far as feathers are concerned, sure a fluffy adult T.rex is not accurate, but the skin impressions we have found are from parts of the body we didn't expect to find feathers anyway. Bristles and quills in the postcranial area are not out of the question though and that's why S. Brussate's book has the particular illustration.