I've worked in teaching that age group for a long time and in my experience, the story told by your son just doesn't ring quite true. I have only ever once come across a teacher who screamed f off to a student and he was, to be perfectly honest, sectioned soon afterwards.
None of this may apply to your son. He may be a paragon, but in my experience, the default setting of 16 year old students is lying. Most of them do it as a reflex. They will deny everything, even if you have a room full of witnesses and cast iron evidence. I've seen them lie to their parents, lie to their teachers, lie to their friends. I've had students and in work copied from their mates, who copied it from the internet. I've watched them insist that the work is their own, even when confronted with the original and the website it was cut and pasted from. I've watched them do this in from of their parents and senior members of staff. I've seen them start formal complaints based on the blatant lies they told. I've even seen them appeal to the exam board when their cheating has been discovered. They seem unable to back down. What distresses me is the parents are often confused when they discover what thir children are like outside their influence. At home they may be loving, well behaved kids, but at school they seem to mutate into something unrecognizable.
Another thing to consider is that it can be dangerous for teachers to swear at students these days. I once faced down an agressive student, a normal daily experience, only to discover he had stabbed another student later that day. If I had sworn at him, chances are that he would have stabbed me instead. So many of them have really poor impulse control, it's not worth antagonising them.
So with apologies for the cynicism, here's a few points to consider:
Did the teacher actually swear?
If so, what did she actually say?
Did he just wander into her classroom and sit down as prearranged?
Had she told him not to earlier in the day?
Had he annoyed her earlier in the day?
Was there a class going on that he interrupted?
Was he asked to wait while the teacher finished her conversation (confidentiality issues may be involved)?
Did he just log onto Wikipedia?
Did he also have a game going?
Did he have other websites going?
Was he asked not to log on to that machine?
Was there a reason why it was inappropriate for him to be in the room at that time?
Had she asked him to leave and he ignored her?
Had she asked him to log off and he refused?
Was he alone?
Did he have one of his more dubious mates with him who was causing some trouble?
Did your son speak to her?
If so, what was his language like?
I suspect there is a kernel of truth in the story. He went to do some work and the teacher got mad at him. He may be telling the absolute truth. If he is then you absolutly have to start a formal complaint, the teacher's behaviour was beyond the pale.
I don't want to deamonise your son. But believe me, I bet you find what he is saying isn't the complete truth.