I believe this is the disconnect between your argument and the prior commentor's comment. This falls under "Note this is not the same as ignoring someone's expressed choice (when being directly addressed) if they have an issue with certain words." The issue is whether the person speaking should know and consider guys to be gendered, and possibly offensive. The fact some people are saying it's not gendered is evidence that's it's ambiguous to some people. To assume someone was purposefully misgendering you without knowledge of whether it's an honest mistake, as we've seen it might be, is not conducive to communication.

> Because I personally know people who see 'guy' as a gender-specific word - and because the dictionary says "guy" means "a man" - I know i'm not going to ever call a woman "guy", because it may offend them.

Which is fine, but you've been presented with evidence that all people don't necessarily have that same knowledge. You can continue to assume that this knowledge must be universal and people that act in opposition to it are doing so purposefully and without regard for the feelings of others, or you can extend the benefit of a doubt, and assume until further evidence to the contrary that they are misinformed about what you believe to be true. I believe giving the benefit of a doubt it more useful and leads to better outcomes in almost every respect.