When Is McCarthyism Acceptable?

I recommend that blacklisting someone for political opinions requires both of the following two criteria:

1. It must be serious. To use Thomas Jefferson's phrase, the political opinion should either pick your pocket or break your leg.
2. It should be obviously wrong. In particular, we must assume that an opinion with the support of at least one major party at the time is not obviously wrong. (There are quite a few opinions whose wrongnesses should be obvious but aren't.)

If we apply the above criteria to the gay marriage controversy, we see that neither side is serious. At most the denial of gay marriage causes gays to feel dissed. We also see that opposing gay marriage is not obviously wrong and was even less obviously wrong in 2008.

On the other hand, blacklisting Communists in the 1950s was allowed by the first criterion but might not be by the second criterion. (Is it possible for something to be non-obvious but not obviously non-obvious?)