I'll add my two cents:
I have never been a member of the Communist Party. Nor do I seek one.
Buuuut, the effort to "root out" Communists in the government is done under the auspices that they are subversive simply for the benefit of a foreign power.
Although I do know that some radical Marxist groups are sympathetic to Communist governments that are very much juxtaposed to liberal Democracy (take N-K for example), the Communist Party, with a big or little 'c' is not one to advocate subjugating the country to another nation.
As much as it would irritate these right-wing nationalists to admit it, the left-wingers are just as patriotic as they are. The Marxists desire to improve the nation is just as strong as those who like to wrap themselves in the flag at every opportunity of public expression.
I think the examples are abound, even going back to the McArthy era and before, where many through-and-through Communists were still primarily seeking to restore equality into the society, through women's suffrage and equal rights to racial minorities.
It's a darn shame that "internationalism" gets so tied up with party unity and party [what's the thesaurus entry where you just accept that's passed on from above??? Stick that here]. At one point it certainly was the same as the proclamation that "all men are created equal, that they are endowed by their Creator with certain unalienable Rights".
In a single word: equality.