Can an author have a public opinion on a controversial matter? I posted about the Ferguson case on my private Facebook and a reader went over-the-top. While it cost me a reader, I stand by what I said (which was neither in favor or against the verdict). It got me thinking that if an author has a measure of renown, will they be forever constrained to keeping their mouth shut about issues that, while controversial, are important? That would seem like a waste of influence to me.
There is no right or wrong answer here. There's only the measure of how much you're willing to risk for posting your opinions. You have every right to say whatever you want on your blog, up to and including posts that are racist, sexist, xenophobic and poorly spelled.
In exercising that right, you also tacitly agree to the consequences: readers may unfollow, unlike, and/or respond strongly to your opinions. Whether they continue to buy your books may be a very real concern.
Frankly I'm not interested in what a rock star has to say about Africa (and honest to god, I wish that man would learn some facts before going all We're Here to Save You) and I'm also extremely uninterested in what a movie star has to say about political matters, but I fear I am the exception since people with a lot of profile tend to get attention for every issue they want to speak on.
Am I going to stop buying U2 albums or seeing George Clooney movies? Probably not. BUT, and here's the great exception: I can't avoid seeing the promotions for U2 albums or George Clooney movies. I can NOT see anything about your book if I've stopped following you on Facebook and Twitter because you said something I thought was racist, sexist, xenophobic or poorly spelled.
You say it's a waste of influence. I ask you: what do you want to spend your influence capital on? Comments on current events or getting people to buy your book? It's your choice. Just understand you ARE making a choice when you post opinions on divisive topics.
On the other hand, you also get to find out who's nuts among your Facebook friends and Twitter followers. That's always an interesting byproduct of a post like that.
And I'm assuming that your posts are well-reasoned and articulate, that the writing is clean and cogent, that you are writing to explain your position or persuade others to join your position. If you are writing to be bombastic or for click-bait, well, even if I agree with everything you say, I'm still removing myself from your radar screen.
Short answer: sure, post away but be prepared to cough up the price of the fall out, if any.