Songs about the "good old days", reminiscences, etc. tend to be taking a happy image, a nostalgic theme and they *simply* say how marvellous that time/moment/image/feeling was.

There could never be anything wrong with that.

A song that then tips over into a sentiment like "Now, it's changed, full of strange people, I don't like it, wish they'd all go home" is unacceptable. Immigrant folk may be trying, reasonably, to have happy lives and experiences that they could write a reminiscent song about. Why shouldn't they be respected for that, and supported? People are entitled to hold negative views of sections of society if they must, they are to be discouraged from singing about their prejudices in a public space.