It is certainly easy to understand why people who are not familiar with this usage would think it's not gender neutral. English speakers generally agree that "guys" in the third person refers to men, so it is unexpected that in the second person, it can refer to people of any gender. As the urban dictionary post suggests, it can even be used when there are no men addressed.  But this is the way my (and other varieties of) English use this word.

The views expressed in the articles and posts I have attached are widespread. Supposedly, speakers who use "guys" as a gender neutral term are either intentionally creating an environment that is unwelcoming for non-men, or they are too stubborn to change their use of the language. The Fast Company article goes as far as calling this usage a "habit", rather than a variety. Both of the articles attached suggest that the world would be more welcoming if speakers of this variety would simply try harder to stop using this phrase, while the Urban Dictionary article suggests that the phrase suggests a sexist bias (in my anecdotal experience, men and women are equally likely to use "you guys"). These are all legitimate reasons for feeling excluded by this usage when someone is not familiar with it, and I understand why somebody's knee-jerk reaction would be to call it "bad" and to call someone defending it “wrong”. It is interesting to note that the usage of “you guys” is associated with geography more than any social class or group, and that it is widely used throughout the US. This suggests that negative responses to this variety likely stem from a genuinely held belief that it is wrong, rather than an attitude towards the people that use it.

I certainly understand why some people have the views that they do, and I think it would be respectful to make the adjustment around people who ask for it (i.e. if a specific person expresses discomfort with being included in the word "guys", I would try to avoid using this term around them). However, I also think more attention needs to be given to the fact that this is a linguistic variety, just like "y'all" or "youze". Using “you guys” regardless of gender is no more of a ‘habit’ than using “coke” to refer to Pepsi products. While it may be polite to try to avoid the term in some circumstances, we should also acknowledge that it is a part of many people’s English, and we should recognize that no harm is intended by it.