Here is the definition of political correctness: 

"The avoidance, often considered as taken to extremes, of forms of expression or action that are perceived to exclude, marginalize, or insult groups of people who are socially disadvantaged or discriminated against."

Taken to extremes is the key phrase.  

The phrase "Come you guys" is "offensive" because it "excludes" women.  It is an innocent, common phrase.  Yet if I was a professor at some of these liberal colleges filled with snowflakes, I could get in serious trouble.  That is what is meant by political correctness--at least when I use the term.