"Regardless of etymological technical "truths", can you really say with intellectual honesty that there's no masculine connotation inherent in "guys"?"
I'm sure there is to certain people. But to me, my family, friends, and coworkers I have not found it to be the case, no.
In fact, I hear female coworkers use the term neutrally every day. We as a team even use the term over conference calls with people all across the country and I have yet to hear anyone take issue, offer correction, or purposefully use alternative terminology.
I simply don't see this as a problem, nor can I understand why it needs to be purposefully corrected. It's the same PC attitude that causes people to take issue with those who call African Americans black. To me, black is a more useful term. If it wasn't in my repertoire, I'd have no way to distinguish Idris Elba from the rest of an essentially all white cast ...
Here's a fun test. Tell me which gender connotation the following terms hold: Cheerleader, Usher, Flight Attendant, and Comedian. If you said female, male, female, male, you'd be wrong as all are gender neutral.