I believe it’s in the Living the Parsha series, Rabbi Yaakov Bender relates a story from when he was in the Mir yeshiva. A bachur got into gambling, and not only was he gambling, he was drawing others in as well. R’ Shmuel Berenbaum zt”l refused to expel him from the yeshiva! A group of bachurim pleaded with him to kick the boy out, but he refused. Instead, he met with the bachur, and worked 1-on-1 with him to solve his problems.
This is how the big Rabbonim deal with these things.