I'm with Stavenger Bill on the 1798 songs - the United Irishmen uprising of that time was not a blatantly sectarian movement, and people of different religious denominations fought alongside each other. Some of the songs about that time can be quite heavy-handed, but most are interesting, although I wouldn't class them as historically accurate - even if they do deal with events that happened, we're still getting propaganda and bias, as we do in every song.
On the other hand, I am not at all comfortable hearing songs that are either deliberately sectarian and provocative (from whatever group), or songs that promote or glorify terrorism, or those that make murderers into martyrs. But then, I supppose I don't have to listen if I don't want to...