This is true, and was known to Ali, and he in fact made no secret of this heritage - was properly proud of it - early on. He also was apparently less affected by racism while younger, telling folks in Moscow when questioned about racism in the USA that we had some very smart people working on it and he was sure it would be taken care of.

Later his Irish heritage and confidence in the government's ability to deal with racism both receded a bit ... not sure how manipulated he was but did become a sort of poster boy for a different point of view, which make the above two facts rather interesting.