Let's forget about the stupidity of the argument on semantic grounds (the term antisemitism ONLY means hating Jews.) Let's pretend it means "hating Semites" like you claim.
1/
If they descended from Canaanites and Jebusites, then they are not Semites - but Hamites, according to the Biblical list of nations in Genesis. So your argument fails off the bat.
(Of course, they are not, but let's keep going.)
2/
Of course, if they are Ishmaelites, that means they aren't indigenous to Palestine, but to Arabia.
3/
Which do you choose?
/end