A nice compromise that I've appreciated in the classes that I've taken - have strict deadlines, but offer X days (say, 2) of a no-questions-asked extension. It creates the clear expectation that work be turned in on time, but offers a small relief valve for one-off problems.

The problem is that this adds extra bookkeeping for a professor who's already busy with everything else going on, which gets back to the original poster's point of becoming everything that they hated.