Walk away–just as you would do if there were a company selling credit cards or any other group on campus that you’re not interested in.
Being aggressively approached by a religious group is a serious problem on many of the Campuses in the United States. Some groups have invited people into their churches and then berated their religion. Others are quite inviting and appropriate at the same time. They let people understand what they are about and then they give them the freedom to come and go as they please.
Some are cults, a serious issue. Any group that tries to deprive you of sleep, makes unreasonable demands on your time, or tries to seclude you from family or friends is one to avoid.
Most campuses have a Campus Ministry Association on the Campus which accredits religious groups as approved religious organizations on campus and sets the boundaries for proselytizing actions. Check with them to see if the group you cite is one which has been a problem on campus before, or if they even belong on the Campus at all. Also report any untoward behavior to a University official or to the Campus Ministry Association. They should have your back here.