Well I know mate, and so they should. Whilst I think it's probably not the best thing to do, there's far too much nanny-stating going on in the World I think. People as I say should look into their hearts in all situations and do what they think is right. Using the behaviour of other fans, or other people in life as a benchmark though isn't the best way to make a decision I don't think. You say to your kids "I don't care that Tommy was throwing dog sh!t at the girls, if he was throwing himself off the cliff etc etc" and it's the same with grown ups.
Not always easy when your surrounded by your mates and loads of other fans, but I'd like to think I wouldn't sing something I thought was wrong. Those fellas will over time I guess make a decision based on their hearts, i'd just be a bit disappointed if it became an ironic "yiddos" type chant, or a "who the feck are Man Utd". I just think Liverpool supporters are better than that. If we (or they I probably don't have the right to use "we") take the p!ss it's funny. There's a big difference.
Like I say though, I'm not trying to tell anybody what to do. I'm just giving my opinion.