What are the parameters for not associating with those who commit evil deeds? And is it obligatory to isolate the person himself, or to isolate the state of his committing evil deeds while denouncing him?

One should not sit with someone who is committing an evil act while they are engaged in it, due to the Almighty's saying: "And He has already revealed to you in the Book that when you hear the verses of Allah being denied and ridiculed, do not sit with them until they engage in another conversation." However, there is no harm in sitting with them at other times. If you are unable to stop the evil, then you must leave the gathering, except in cases of necessity, while denouncing it in your heart. As for sitting with transgressors when they are not committing an evil act, it depends on what is beneficial: if there is hope of reforming them, then sitting with them is more appropriate. If they are deterred by abandonment, then abandonment is more appropriate.