I can't even imagine how much protein one would need to consume to become dehydrated - and it would need to be intentional dehydration, purposely gorging on protein, while intentionally avoiding drinking water.

As an example, the annual Nathan's Hot Dog Eating contest was held a few weeks ago. This year's winner ate 58 hot dogs in the allotted 10 minutes. Each hot dog only has about 5 gr protein, but of course it's served in a bun which provides approximately another 3-5 g protein. They can drink water with it, but mostly they don't take the time to drink at all, just dunk the hot dogs in water to soften up the bun so they can swallow the hot dog and bun with very little chewing.

So there they are eating 58 hot dogs (x5 g protein) along with 58 buns (x 3-5 g protein) for a grand total of 464 to 580 g g protein. In 10 minutes.

They'll probably throw up afterwards due to the sheer volume of food they've swallowed in such a short amount of time - but that's still somewhere in the neighborhood of 10 TIMES the amount of protein they want to limit everyone to in a day... and yet they were not even drinking water with all that protein, only dunking their buns in water to make them easier to swallow. Somehow, they still do not become dehydrated on 10 times the recommended daily protein limit.

I hardly think anyone is going to become dehydrated by eating 100 or even 150 g protein over the course of a day, even if only drinking when they happen to be thirsty.