This was right after m4 was called gross and was said only to be good for special purposes, that it was to be avoided in general and better alternatives should be used instead. Then it says m4 is like immigrants. If it's a song reference, it's a rather poorly chosen one.

This is yeah, probably a cultural mixup. There's a fair number of people in the US who view and characterize immigrants as freeloaders, when the truth is they work harder than "natives" and our economy depends on them. And like a sibling comment says, it's a reference to a line from Hamilton, which celebrates in lots of ways the US' diverse heritage.