Thats not evidence. That is just a claim made by the professor, which is denied by the former student and which, according the the article, is not reflected in the tone of the emails exchanged at this time, either.
Isn't eye-witness testimony considered evidence? Maybe the professor is lying, true. But also professional emails tend to be more cordial than in-person conversations. In terms of motives, the student has more motive to lie than the professor, since the professor has nothing at stake.
The nice tone of the professor’s emails (after the run-in) could be also proof of her goodwill. While student showed his lack of self control on twitter.
This is just a different aspect of the same facts.
> The nice tone of the professor’s emails (after the run-in) could be also proof of her goodwill.
What was nice about it?
> student showed his lack of self control on twitter
I don't see a lack of control on Twitter. The student wasn't talking to the professor, and there is nothing inappropriate about their Twitter comments as reported, beyond the cartoon which IIRC the advisor didn't cite.