why do so many discussions turn contentious?

just venting....why do so many discussion posts need to turn  contenious and nasty?  do you guys find that constructive and/or enjoyable?  I have no clue who or how this forum is moderated, but I sure would love to see a stop to that...it makes me feel like this hobby is dominated by total jerks.

Can't we play nice, share OPINIONS and OBSERVATIONS, realizing that  they often are subjective and biased.  
"if you dont have anything nice to say, say nothing"?  If you wish to disagree, do it in a constructive and mature fashion, no need for "argument ad hominem"...

with all the chaff, one must waste so much time finding the wheat, figuratively speaking.  

I doubt my writing this will change anything, but, like most social media, people writing to others without facing them does not bring out the best, sadly......