The effectiveness of an argument is measured by the extent to which it moves people towards your side. Obviously, if you make an argument that repels people, no matter how logically valid it is or you think it is, that "negates its effectiveness".
There are no prizes for being morally correct, though I wouldn't argue that people who want to ban abortion in cases of rape are moral.
It would be equally applicable to a Roman Senator who in 149 BC would say "hey, maybe we shouldn't destroy Carthage because they haven't done anything wrong".
Making arguments is trying to get the audience closer to your POV, nothing more.
The effectiveness of an argument is measured by the extent to which it moves people towards your side. Obviously, if you make an argument that repels people, no matter how logically valid it is or you think it is, that "negates its effectiveness".
There are no prizes for being morally correct, though I wouldn't argue that people who want to ban abortion in cases of rape are moral.
It has nothing to do with liberalism though.
It would be equally applicable to a Roman Senator who in 149 BC would say "hey, maybe we shouldn't destroy Carthage because they haven't done anything wrong".
Making arguments is trying to get the audience closer to your POV, nothing more.
You willing to bet your immortal soul, and the lives of innocents on that?
Do you think it is impossible for a valid argument to not be effective in your aim, which is persuading people?
Of course there are. And there are many bad, invalid and fallacious arguments that are effective.