Do you not see the irony in quoting a dictionary definition to refute an argument in favor of using words in non-standard ways?
Do you at least see it now?
i·ro·ny [ahy-ruh-nee, ahy-er-]
noun, plural i·ro·nies.
1.the use of words to convey a meaning that is the opposite of its literal meaning: the irony of her reply, “How nice!” when I said I had to work all weekend.
2.Literature.
a.
a technique of indicating, as through character or plot development, an intention or attitude opposite to that which is actually or ostensibly stated.
b.
(especially in contemporary writing) a manner of organizing a work so as to give full expression to contradictory or complementary impulses, attitudes, etc., especially as a means of indicating detachment from a subject, theme, or emotion.
3.Socratic irony.
4.dramatic irony.
5.an outcome of events contrary to what was, or might have been, expected.
But seriously! Back to the actual derailed discussion. Using "literally" to mean "figuratively" is not wordplay. And yes, language can evolve over time and words can take on more than one meaning. But when a word means both one thing and the complement of that thing, that word has no meaning whatsoever.
It's not just that they're opposites! Black and white are opposites, but there are many things that are neither black, nor white. But if something isn't meant figuratively, then it is meant literally, and vice versa. It's like you're arguing that it would be OK if one of the definitions of "off" was "on".
"Honey, why are all the lights in the house on?! I asked you to turn them off before you left!"
"Oh, you meant 'off' off! I assumed you were using the definition of 'off' that meant 'on'! My bad!"