...We saw it last night at Wrigley Field.

We’ve come to expect mistakes over the decades at Wrigley. Mistakes by the Cubs, mistakes by outfielders chasing windblown fly balls lost in the sun, not mistakes by umpires.
Last night, those in attendance and watching on television were treated to a pair of serious umpiring mistakes. The first mistake  prolonged the game. Vacation replacement umpire Chris Conroy called David DeJesus safe on a sacrifice fly. DeJesus never touched the plate. Molina clearly tagged up. The only thing Conroy got right was his positioning.
In the 10th, second base umpire Bill Welke was also in position and somehow managed to miss the obvious tag on Tony Campana on a stolen base attempt. This is an 11 year veteran who missed the call. He was also in an appropriate position and had a good look at what happened.
Sure, these guys are human and because of that, umpires are going to make mistakes. However, these guys are supposed to be at the very top of their profession. Whatever  Major League Baseball’s standards are, they are not high enough. Every week, sometimes every day, you can find examples of missed calls. Seems to me that problems like we saw in the first and tenth innings last night occur far too often.
Other  sports are pretty ruthless in weeding out substandard officials. The NFL grades tightly and those that don’t measure up are not retained.   Essentially the same thing happens with BCS level football in the NCAA.
College basketball also weeds out the ranks with efficiency. Get it wrong too often, and those good D-I and D-II assignments vanish.
The umpires union is strong, but I would think that the majority good to excellent umpires would want to do something about the few that are defaming the profession.