Irregardless in English

I don't know where we got this idea that those negatives have to be multiplied, which is what they would do in mass, to create a positive. For why they can't be compounded instead of multiplied to cancel each other out, has never really been explained. Weh've not really been given an organic reason to dislike the word, other than we've been told to dislikeit. People very selectively apply logic to language. It's great when it works. But of course, language isn't logical. I want to focus on with irregardless is wat the question of, why have unremorseless and unmerciless been removed?