There's a luxury to being politically vocal, and it's seated in your perception of your personal safety. It's one big reason why men dominate the discourse and feel entitled to highjack, derail, and weaponize it. They're not worried about what they say online following them offline. Those who do not identify as male do have to worry about that in the same way we have to worry about where and how we park in a public garage, how we have to have our keys in hand before we reach our destination, how we continually monitor the number, distance, and sobriety of men in our immediate surrounds.
Because social media is intertwined with our offline lives, we expose too much personally-identifying information to the masses. Often without realizing it because we're being social. As authors, we're being social because we need to increase our visibility, because the more people who know about us, the more people who know about our books, the more books we'll sell. It's the closest we can get to a "sure thing" for sales.
So what does that have to do with us being politically outspoken online? These days, political activism lights a beacon for those of nefarious intent. They suddenly have a reason to take a closer look at you and what you've posted. Do you live alone? Do you have a pet that might defend you or that might make you more accessible? Do you have routine days? A regular coffee shop habit? Do you reside in a small community where strangers might be noticed? What about a city where everyone is a stranger? Are you in the frequent company of others or are you a loner? Spouse? Children? What school do they attend? What do they look like? What are their social accounts? You didn't file for copyright of your works with your real name and address, did you? What about that required mailing address in the footer of your newsletter? Used a PO Box, but still in the same city? What about your property tax records, they wouldn't happen to be under your name or a family member's, would they?
As states resume using vigilantes to police their neighbors and reestablish witchhunts in the 21 century with cash bounties, the threat to personal safety is going to get worse. Worrying about whether your political opinions will negatively impact your author brand is pointless if your life's been destroyed because you made a stand online.
Now, you may scoff and think, "Wow, Debby Downer, way to go with the doomsday hysteria." That's fine. That's also a testament to your perception of your personal safety as well as your privilege. Good for you. That means you have a plan for dealing with online harassment, right? You're one of those authors whose day isn't ruined because of one bad review, let alone dozens, or hundreds, right? You're ready to invest in remedying the crashing of your online store/website? You're ready to be dropped by your agent/publisher based on manufactured drama (truthful or not)? You're solid on the steps you'll have to take if the harassment moves offline, right? You've brushed up on stalker laws...and what they don't protect against, right?
This isn't to say you ought to sit down, shut up, and take what's dealt to you. It's a reminder that as an author, you've put yourself in the public space--whether you've written one book that's sold ten copies, or written ten books that sell a few hundred thousand copies each--which makes you a more "interesting" target to those who want to make trouble. It only takes one asshat with a modicum of skills to rock you back on your heels. Are you emotionally, physically, and financially prepared for it?
If, however, you are comfortable with your safety and feel you're at low risk for harassment, then by all means, drag the fools as politely or brazenly as suits you. Be a voice for those who cannot.
Regardless of whether you get political online or not, ask yourself, is there a better, more effective way to advance your cause(s)? Does volunteering an hour a week offline do more good than tweeting an opinion? Sure, the former is more inconvenient for you, but it's also more impactful, isn't it?
While it's great and noble to organize and fight for a more perfect union, take a beat to figure out if shouting into the void is worth the risk to your safety...and the safety of those around you. The answer might be yes. Then again if it's no, there is no shame in holding back.