Why did the Commonwealth Parliament ban theatre?

I've known for a while that theatre was banned under Cromwell, because the Puritans disapproved of it. What was their objection? Wikipedia adds this information: > Pastimes such as the theatre and gambling were also banned. However, some forms of art that were thought to be 'virtuous', such as opera, were encouraged. These changes are often credited to Oliver Cromwell, though they were originally introduced by the Commonwealth Parliament; and Cromwell, when he came to power, was a liberalising influence. Assuming that's true, in what sense is the opera more virtuous than the theatre?