One of the most common pieces of advice given to people who both blog and have a professional online platform (authors, musicians, bespoke-weasel-waistcoat tailors, &c.) is to avoid discussing politics and religion; indeed it is such pervasive advice that some give it to anyone as the answer to any situation. However, as with many rules that can be expressed in a brief sentence, it is usually given without an important modifier: without reason.
Politics and religion are both emotive topics. While there are no doubt those who disagree about the exact value of π, their dispute is likely to be over abstruse questions of mathematics rather than over whether it is evil to use a particular method; and so with most discussions of hard science. However, the same is not true of politics and religion; both speak to our identity and sense of worth in a way that preferring string theory to loop quantum gravity does not (Sheldon Cooper not withstanding). They are also things that most people have at least a lay interest in.
To express opinions on benefit changes or abortion is to risk inflaming your audience. And, the human mind tending to reduce things to convenient labels, each time someone disagrees with you about one thing, is another moment in which they might dismiss all your opinions and actions on the basis you are WRONG. So, avoiding controversy is a sound way of not losing potential readers/customers/&c.
However, as frequent visitors will know, many of my posts touch on religion and politics; for three reasons:
My core audience enjoy considering social and moral questions: I write stories about individuals, but many of them grew from the question “What if society was this way?”; even Greenstar, my lightest work, deals with a fascist global corporation engaging in genocide. While it is possible to wear a waistcoat without having any interest in ethics, my fiction is less likely to appeal to people who don’t ask “What if…?”
The human world is formed from politics and religion: as this article by Brian Basham shows, writing about the real world makes imaginary worlds deeper, broader, and more nuanced.
I want a better world more than a bigger pay-check: for me, the improvement of the real world is more important than selling more copies of imaginary ones; so, if expressing my opinions loses me a few potential readers, it’s a price I consider worth paying.
Of course, this is only my answer, and there is a huge difference between what an opinion is and how it is expressed. I advocate neither publishing contentious opinions for the sake of it nor indulging in baseless abuse.