You could inform him the the "American Dream" of the white picket fence, lawn, etc. is just that.....a dream! That dream is just about over. You could try to reason with him but that would most likely not work.
"Reason is not automatic. Those who deny it cannot be conquered by it. Do not count on them. Leave them alone." - Ayn Rand
I believe passionate people are sometimes labeled "Assholes". I catch myself getting so worked up about something I am passionate (and sometimes not so knowledgeable) about and come across as a real jerk. It isn't intentional, it just happens. A true friend of the "asshole" should try to correct his or her behavior in a nice way. Chances are they don't even know they are being an a-hole.
I looked up Guava and see that it is tropical. I am in zone 8 in the southeast (I should have mentioned that). The fruit does resemble young Guava fruit.
There is a grove of these and they are intermingled with some Black Cherries, Wild Plums and Dog Roses.