It's a witchhunt if it's merely an accusation without evidence. In this case, Emil Micheal publicly confirmed the veracity of the Buzzfeed report and apologized. In another example that was labelled a witchhunt, Brendan Eich was on public record as supporting an anti-gay proposal.
It's not a witchhunt if the people in question are attacked over what they do or say and not over unproven allegations.
As for proportionate, that's quite subjective. It's not a coincidence that the subjects tend to be fundamental issues of ethics and ideology over which opinions vary wildly.