Marxism has nothing to do with it. Ken's point was that Keith throwing the F-word at people who disagreed with his abortion stance was ironic, given the Nazis' disposition against abortion.
The issues I have with the remainder of your post are not linguistic or moral, but logical.
Rights are human constructs, by humans for humans. One human 'right' is the right to food. It might not impel anyone to give someone else food - but you breach someone's rights if you prevent them from having food. So your logic doesn't prevent abortion from being a right.
" Apart from rights, there is plain old responsibility. Responsible women don't carelessly get pregnant. If an unexpected happens, responsible women keep the baby and deal with it. "
Responsible women? I think you are forgetting something here...
Gay Marriage...A civil court can refuse a gay couple marriage permission but NOT where there is a presumed right to equal treatment under the law. That's what Gay Marriage rights means. You would for example, not be allowed to marry while already married, whether gay or not - but that would not infringe the right to Gay Marriage because a straight marriage under these circs wouldn't be allowed either. So in that sense there IS a right to gay marriage.
Your argument would allow a business to serve only white people, on the basis that there was no 'right' to be served. Do you really want to use the line trotted out by racists and bigots? The days of signs like "No blacks" or "No Irish" (often seen in UK accommodations a few decades ago) are thankfully gone, and hopefully for good. And it was anti-discrimination laws that did it.