A Google search for Kennedy and Sirhan and immigrant ...turns up about 21.
Sirhan Sirhan emigrated to the United States in 1956, and was a fanatical Palestinian nationalist,  although he was raised as a Maronite Christian, and was a citizen of Jordan. His crime is an obvious example of the "dark side of diversity."  Here's what Peter Brimelow  said about him in the Afterword to Alien Nation. 
For example, Jacquie Miller in the Ottawa Citizen worriedâ€”all too presciently, for what it is worthâ€”that "phrases can be plucked out of Brimelowâ€™s book that, shoved only slightly out of context, provide ammunition[for the inevitable charge of racism] She instanced my references to high black crime  and Laotian welfare rates. Miller also felt that the "credibility" of my account of Robert Kennedy's ludicrous underestimate of Asian immigration resulting from the l965 Act (p. 78) somehow suffered from what she described as "a typical slur": my adding that "tragically, Robert Kennedy himself was to be assassinated by an immigrant counted by the INS as Asian."
My first reaction to this sort of thing, of course, is incredulity. I believe truth should be an absolute defense, as it is in libel law. Laotians do have disproportionately high welfare rates  etc. And I said "tragically." didnâ€™t 1â€™
Still, I recognize a problem. There is no point in repelling readers, at least those who show Ms. Millerâ€™s symptoms of open-minded ness.
The problem, however, is not easily resolved. The truth, we are told after all, shall set us free. And it is precisely because of the mediaâ€™s flinching from facts that many Americans are unaware of the immigration dimensions of major contemporary public policy dilemmas . It is because Americans are never reminded of the Jordanian origins of Kennedyâ€™s assassin, Sirhan Sirhan, that they donâ€™t think to put him at the head of a list of infamous immigrants to counter the immigration enthusiastsâ€™ silly ploy of reeling off, in place of argument, the names of distinguished immigrants. In fact, many Americans canâ€™t think of a list of infamous immigrants at allâ€”another example of the one-way nature of the immigration debate.
The LA Times reprints an article by Steve Lopez , in which he interviews Juan Romero, who as a young busboy at the Ambassador Hotel, comforted the dying Kennedy, and actually manages to put a pro-immigration spin on it.
Juan was convinced he was supposed to find a way to express the hope Kennedy represented for him, but he couldn't find the words.
During the debate over California's Proposition 187, he felt that people were taking one look at his brown skin and figuring him for a freeloader. He wanted to scream that the ballot initiative was proof we needed another Kennedy, but he couldn't find a stage.