From the UD's definition #6 of "irregardless":
Coined in the United States in the early 20th century, it has met with a blizzard of condemnation for being an improper yoking of irrespective and regardless and for the logical absurdity of combining the negative ir- prefix and -less suffix in a single term. Although one might reasonably argue that it is no different from words with redundant affixes like debone and unravel, it has been considered a blunder for decades and will probably continue to be so.
Check out http://english.stackexchange.com/questions/19197/what-words-sound-like-opposites-but-are-synonyms.
You have to teach them that it's not preferred. Of course, teaching is hard work, and hand-wringing and whining isn't.
This argument about a single mythical english language has been going on for hundreds of years, and will for many more. We've had a few centuries of relative stability with some dialects of english after the invention of the printing press.
The invention of e-mail and texting will change the picture again.
Some people don't want to recognize that or bother to change.
/johnny