Good point, but I think you have it totally backwards: the usage in this case is audience-correct but not dictionary-correct. In fact, I think you guys is a good example where "language rules" have not caught up with usage.
An important thing to understand is that language is not governed by a strict rules, such as compilers, it's based on a social contract, in fact Wittgenstein pushed this idea to its extreme by declaring that a word's meaning is its use (this idea is not without it's own problems, of course).
I think the problem here is not that the people who object to the usage can understand the correct usage (in fact such usage is prevalent among the high-school crowd, which you can readily observe if you teach) but that they see it as sexist usage, e.g. similar to objecting to use of stewardess. I would suggest the correct approach here would give them the similar cases of y'all and you lot, not as a fry lecture but as a frank discussion.
An important thing to understand is that language is not governed by a strict rules, such as compilers, it's based on a social contract, in fact Wittgenstein pushed this idea to its extreme by declaring that a word's meaning is its use (this idea is not without it's own problems, of course).
I think the problem here is not that the people who object to the usage can understand the correct usage (in fact such usage is prevalent among the high-school crowd, which you can readily observe if you teach) but that they see it as sexist usage, e.g. similar to objecting to use of stewardess. I would suggest the correct approach here would give them the similar cases of y'all and you lot, not as a fry lecture but as a frank discussion.