Here's a short excerpt, but do read the whole thing:
Nationalism is patriotism on steroids; it is patriotism degenerated into jingoism and chauvinism. It is near idolatry of country and often appears in mixing celebration of nation with worship of God. Patriotism thanks God for the good of one’s country and asks God to “mend its every flaw.” Patriotism is honest about the country’s failures and urges leaders to push on toward better achievements of its founding ideals. Nationalism rejects all criticism of country as almost (if not exactly) treason. . . .
Idolatry is such a subtle and seductive force (nobody ever thinks they are engaging in it!) that Christians ought always to be on guard against it. It is best to steer clear and wide of it. That’s why I prefer not to have a national flag in any worship space. While it might not constitute idolatry, it presents that possibility. Too many people even in Christian churches do treat the national flag as an idol. One “good Christian man” I know threatened violence to anyone who removed the flag from the church’s sanctuary.
So, bring out the stones and cast them at all of us who think that the nationalism displayed by far too many who call themselves christians is really just idolatry and worship of a false god. I personally would go even further than Roger Olson in saying that much of what is called patriotism is also veiled nationalism. For example, I don't see how a Christian can recite the Pledge of Allegiance or stand and sing the national anthem. For me both of those are idolatry.
So bring on the stones! You're probably going to get your Supreme Court justice who will cause SCOTUS to endorse the death penalty anyway, so why not do it now? : (