I don't dislike it because it's technically incorrect, I dislike it because it doesn't add anything to the language. The word "ain't," though it gives the impression of being uneducated, nonetheless serves to smooth out the language and help it flow, and may one day be commonly accepted speech. Likewise, use of the word "their" as a gender-neutral pronoun is rapidly become accepted, and in the more distant future may end up replacing gender-specific pronouns entirely. "Irregardless," on the other hand, does nothing. If anything it adds a syllable, making it even harder to say, and is therefor pointless.