Here's a question: was burning anyone at the stake for any reason ever the right thing to do?
Not alive, no. It's no different with the Romans and their twisted manners for execution. There was nothing humane about that. Now, as far as executions go, we know there were, and somtimes are, pressing reasons for those, but the manner of executions as barbaric is unacceptable.
The only thing I will say about the purpose for using those methods was to instill great fear in any individual that dared oppose/challenge authority. I suppose that in the crudest way, it got the point across.