No, it is not an "illegal campaign contribution" as it is not a contribution of anything of monetary value to the campaign organization of the candidate. Making your own ads in support of a candidate is not a campaign contribution, for example, even though it may indeed help that candidate. That is why you see various PACs spending tons of money on their own ads in support or opposition to candidates. I don't know what you mean by "taking active steps to hurt the other side" but FB is free to express its support for a candidate and opposition to other candidates like anyone else. They are not broadcasters and thus not even subject to the old equal time provision that the TV networks were subject to.

