Re: "One solution is to boot a Linux USB stick ..."
Not taking sides because I really don't care.
But I think the accounting software argument was more along the lines that it's harder to switch to Linux because there isn't a Linux version of your already existing accounting package.. Your options are either import x years of data and hope nothing gets lost or stick with what you know even if that means windows too.
I think that was his point, but as I said, I don't care.
It's an operating system, use what works for you. If you care that much about what someone else is using you need to reevaluate your priorities in life.