Free speech guarantees you the right to say it free from consequences. It says nothing about a guaranteed venue or audience. And any college would have a legitimate interest in blocking that material over their e-mail system on a mass scale. It's happened before:
"An estimated 3000 [Michigan State University] students protesting the ban on alcohol at Munn Field tailgate parties resulted in police firing tear gas at the crowd. The gathering was planned in advance by an email spread through the student body email system asking students to gather and protest the ban. The university police informed students, via the school newspaper, that anyone getting on Munn Field would be arrested for trespassing. One student crossed the fence and was arrested by campus police. Shortly thereafter, 30-40 students crossed the fence and when the remaining students saw the police unable to arrest everyone, approximately 1,500 students poured over the fence on Munn field. The students played football, frisbee and played in the rain and mud. The police then tear gassed the students, who then left and went to the University President's (M. Peter McPherson) house. When the students learned the President was not available, they then went to Grand River Ave, and a small riot ensued."
And don't pull the "only conservatives are restricted" card because it is easily annihilated.