shouldn't it be der guter Mensch? because Mensch is masculine
no, it's nominative with article, so weak declension, it's an -e, if it was indefinite or without article then it would be strong adjective declension -er , ein guter Mensch, guter Mensch
I was as confused as you are until I found this (see jess1camar1e simple learning trick) http://www.duolingo.com/comment/556140
Thank you very much for linking to that post
Der gute Mensch von Schechuan
Mensch throws me a little because, growing up with people that sprinkle in a bit of Yiddish, mensch is used to refer only to a good, reliable person, not a person in general.
Isnt it "Die gute Mensch"? Isnt gute feminine?
It's an adjective, so it doesn't have a gender. "Der" is referring to "Mensch."
If Mensch is masculine, why it is not "Der guten Mensch"?
Because this is in the nominative case (and we have the direct article). "Den guten Mensch" wold be the accusative.
This isn't translated as "The good guys"?
"Mensch" is singular, so no.