(Mishnah): One may not sell them bears, lions or anything that causes public damage.

One may not build with them a basilica (used to throw condemned people to their death), a scaffold (also used for putting people to death), a stadium (where condemned people were put to fight and be killed by animals) and a platform (from which condemned people are thrown to their death).

However, one may build with them public and private bathhouses (even though they usually contained a room with an idol and they would pledge money in its honor).

But a Jew may not build the dome upon which they stand the idol.

(Gemara): The Mishnah only prohibited selling them animals that damage, but if they do not damage the public, it is permitted.

The Mishnah follows the opinion of R. Nasan, as the Beraisa teaches...

(Beraisa): It is prohibited to go to see sorcerers, soothsayers, mukion, mupion, mulion, milarin, milaray, segiralon or segilaray (different types of jesters and jokers), because they are considered the company of scoffers, as the pasuk states (Tehillim 1:1), "and he did not sit in the company of scoffers".

And all of these lead to negating Torah study, as the pasuk states, (pasuk 2), "But his desire is in the Torah of Hash-m".