In a discussion in Another Place on this very subject(left wing hymns used by rightwing politicos) something else was pointed out that I didn't know: that Holst(composer of "I vow to the my country") was a life-long socialist.
In view of the intemperate tone of many of the contributors to this thread, let me make clear that of course people can choos whatever hymns they like for their funerals. But equally well, if a song is used on a political occasion it is legitimate to point out the irony if the song originally had an entirely opposite political purpose.