Absent I agree with you about the unconditional love a mother feels, and the need for adolescents to push boundaries, but I don't think that means that a parent should simply accept abusive behaviour from a child of any age.
Indeed it's part of a parent's job to teach a child what those boundaries are, and the meaning of mutual respect, and clearly you succeeded with Absentdaughter.
Ruby I hope you find a way for yourself and your son.
In your position, if there is anyone at your son's college who is responsible for pastoral care, like a tutor or a subject teacher who knows him well, I would ask for a confidential interview to see if there is anything going on at college that could explain his behaviour and to see if they have any suggestions as to how your son could be helped.
I think too that you need to see yourself as the adult guiding your child - in your OP you sound more like a child who is being bullied. Don't threaten your son with eviction or anything like that - just tell him how upset and unhappy his behaviour makes you feel, and that you don't like it. Make sure you focus on the fact that it's the behaviour you dislike, and not him.
As Absent says, he probably hasn't the first clue of the effect his behaviour has on you - and deep down, children don't want to make their parents unhappy, and they do want them to set guidelines.
Good luck 