I am an immigrant and am libertarian... My wife is an immigrant and libertarian-moderate. Both of us are very pro-gun.
Many of the immigrants I know are unfamiliar with guns, but are not hostile to them either. And interestingly, most of them have a very matter of fact attitude towards self-defense - they consider it quite right and understandable, very different from the hand wringing by so many Americans about "how can you take a human life to defend yourself... "
Immigrants are not anti-gun, unless you beat them over the head, and they learn to associate gun rights with your hostility. If you are concerned about immigrants diluting gun rights, make a concerted attempt to reach out to them. I have taken some 18 individuals shooting over the years, men and women, native born and immigrant; they have all loved it and come away with a much greater appreciation for guns and a much better understanding of the RKBA. I suggest that you do the same - you will be surprised at how often people are curious about and want to handle guns.
In the 1780s, when the population of the newly hatched US was less than 3 million, and 80% Anglo, Benjamin Franklin worried aloud about the masses of immigrating Germans, ".. who will soon be so numerous as to Germanize us, instead of our Anglifying them...". Something to think about.