Hmm, couple of thoughts-
1)Why so many letters from 97405-- these tend to be the folks who still believe in the possibility  of good government--  they're less alienated, they are more willing to take part in civic activities, work to make it better, vote, take part in city committees, write letters, etc.
2) Try comparing the blogging activity here on  Civil Comments to the letters that originate in print and I'd say you get a much higher percent of pro-Trumpers here, especially among the anonymous.  I don't know the meaning of this.
3) The result is, I believe , a more active, even dialogue  here, with both sides, or all sides, forced to defend their views against various attacks.  While some of the stuff posted here is pretty stupid or nasty, there are some serious, useful   debates.  And it's instant-- by the time some of these letters appear in print they'll already have been well  commented on here. 
 And happily  probably 100% instead of 32% of my writing will be posted.