I love that "Microsoft has backdoors"...no one credible has said that they have proof of that. They give the US Government early access to vulnerability data...they give those updates to several governments and large corporations early as the result of agreements they have made with big customers. They also let these same entities audit the source code for windows. Look it up. If you have the money and its important to you then, yes, you can audit the windows code base.
"security-conscious people prefer Linux"...That's kind of a sweeping statement. What does security conscious even mean?
To me it sounds like this..."People who talk about security a lot use Linux by and large"..."but some of them are really partial to OpenBSD"..."and lots of Windows security experts really use Windows a lot."
I say that its a shit lifestyle decision because what is it accomplishing? You use this really restricted platform to make sure that people can't track you doing ??? What exactly? Communicating with your team of spy's??? Downloading midget porn??? Why do you think that you can have a single workstation that's good for every security corner case? What in the history of computer security makes you think that is a good idea or even desirable?
Let's take the example of the Iranian dissident trying to avoid the oppressive badies in their weird ass government...what does tails or Linux buy you? You are better off with the "throw away laptop" plan using good opsec and running tor from public places. Don't use it for anything but tor and tweeting your pics of black helmeted assholes. Get a new one as soon as possible. Rotate them with other people. The OS means next to nothing.
People keep conflating tor's uses with every possible InfoSec edge case. The dissident has different needs than a guy trying to make sure that the NSA doesn't catch him posting documents. The whistleblower has different needs than the guy buying drugs.
In all cases applying some critical thinking about what you are trying to do is a bigger exercise than "Winblows is the suxor at securitehz!"
Unix doesn't have a monopoly on security. I'm not saying windows does, but Unix people are kind of crazy about their pet platform.