(R. Meir): It is prohibited to go to a theater because of idol worship (as before the show, they would sacrifice to their idols there).

(Chachamim): When they are sacrificing, it is prohibited because of idol worship; when they are not, it is merely the company of scoffers.

One who goes to a theater (in which they sometimes take people from the crowd to battle wild animals) and shouts (to try and save a Jew that fell to their hands) or if he goes there to take care of public needs, it is permitted; if he encourages them by going, it is prohibited.

One who sits in a stadium is like spilling (his own) blood, (as they sometimes take people from the crowd to battle the animals.)

R. Nasan permits it for two reasons - because he can shout and save Jews and because he can testify for a woman to remarry (if her husband was killed there).