Mr Wu is just a comic song about a Chinese laundryman [as many laundrymen were at the time: hence the term Chinese laundry] whose work is suffering as he has grown careless because he has fallen in love. It's a funny song, with one or two of those suggestive non-rhymes ("Oh Mr Wu has got a funny little eye that flickers, You ought to see it wobble when he irons ladies' blouses" ~ oh tut tut & deary-me!).

Wu is a common Chinese name ~ I have a dear friend called Professor Wu Ningkun.   

That's all. What on earth is supposed to be racist about it, for crying out loud?

~M~