I don't know how much credence to assign the survey.
When our association loses members, the most common reasons given seem to be age/infirmity, work/family schedule conflicts, or unhappiness with level/quality of games assigned.
My hunch is that parent behavior may be more of a factor in decisions by less experienced umpires not to pursue umpiring as a long-term avocation. Umpiring probably isn't fun for people who don't learn to tune out irrelevant noise.
In my own experience, I haven't seen a trend in parent behavior over time. Each year, it seems that zero, one or two games have something ugly happen. Very seldom in a high school varsity game. More often in local tournaments late on a hot day.
Umpires have some power to influence the tone. Being professional, approachable, and courteous has a good effect on the conduct of game participants and fans.