Updated at 22:51 EST (see bottom of post) | Wiley Miller's "Non Sequitur" strip is syndicated in newspapers throughout the country, including the Washington Post. To the extent Miller delves into politics and social or religious critique, it's generally from the left.
Today, the day before Ash Wednesday, Miller's February 21 cartoon was entitled "Divine Intervention" and depicted a bishop in ecclesial dress at a bar, with five empty communion chalices in front of him, being cut off by his bartender (see cartoon below).
It's obviously a gratuitous attack on Catholic priests, but the Post apparently had no problem with it. Miller himself is an equal opportunity offender, having drawn a cartoon in October 2010 that mocked Islam founder Muhammad. When it came time to publish the cartoon, however, the Post refused to print that strip, even though it didn't even depict the prophet.
Update (Feb. 21, 22:51 EST): Wiley Miller emailed me with his reaction to this post and granted my permission to append it as an update for the benefit of his take on my analysis:
A reader just sent me a link to your article on my cartoon today. While I agree with your overall point regarding the hysterical overreaction by the Post (and every other major newspaper in the country) over my "Where's Muhammed" cartoon (ironically validating the point of the cartoon by refusing to run it), I have to ask how you come away from this cartoon with the notion that it's a "gratuitous attack on Catholic priests"? Exactly what issue do you see in this cartoon that is being attacked? The cartoon is nothing more than a word-play gag. There was absolutely nothing of editorial commentary intended in it.
As you noted, I'm not shy about satirizing big targets in society, but it simply is not the case in this instance. If I was going to "attack" the Catholic church, it would have been more obvious and clearly on a specific issue. I don't do "gratuitous attacks" on any specific religion. On religion in general, sure. But if there's something to hit a specific religion on, I will attack that issue, not the religion itself.
I hope this clears things up for you. It never ceases to amaze me what people will read into a simple cartoon. Such is the abstract nature of the beast, I suppose, but more often than not, as Freud famously said, a cigar is just a cigar.