People handle stress in projects in different ways. I find it helpful to use an analogy with electrical components:

stress resistor

Some people shield others from stress. They pass on what needs to be done, but shield the team from negative pressure. They seem to think that passing on stress does not help productivity.

stress conductor

Some people pass on stress to others. They seem to think that the team needs to share the stress they're under themselves to help them prioritize.

stress amplifyer

Some people forward stress to the team with extra emphasis. They seem to think this spurs them on.

I have my preferences, but I actually think neither of these options is either good or bad. The most effective strategy is highly situational, and depends for instance on the individual characters, the atmosphere in the team, and the phase of the project. So, I think a good project manager can switch based on the circumstances.