She saw the student as handing out copyright protected software to students. As such, in her ignorance of licenses like the GPL, she saw this as an example of copyright violation and of encouragement of such. Given the mass hysteria of people like RIAA re copyright and given that obeying the law IS one of the lessons the school should be teaching, she saw the encouragement of such copyright violation as being an actionable offense, which it would have been, were it not for the license. That she was unfamiliar with say the GPL (Have you actually read the license?) IS ignorance. That she was upset with someone encouraging violation of the law to her pupils, as she saw it, was exactly what it should be.
Had she seen the student handing out free crack samples and being told that someone had encouraged him to do so, would she have been overreacting?
Just as you make a laughing stock of the whole "free software" movement?