If there's a good reason for the change (inflammable came first from inflame, then flammable to avoid confusion) then it's fine for it to catch on. "Irregardless" doesn't need to exist; it causes more confusion, not less, because it's one of those "trying to add emphasis by making it the opposite" situations, like when people use double negatives to mean "really negative" or use the word "literally" to mean "not literally".
It ought to be discouraged, not shrugged away by saying "well, language changes!". Not all change is for the better.
It ought to be discouraged, not shrugged away by saying "well, language changes!". Not all change is for the better.