Honestly, if you're a Trump supporter, do you even care about these remarks? John McCain isn't exactly loved in the fringe far-right that loves Trump, and if you are the kind of person who honestly would vote for Trump you've already managed to ignore or agree with every other despicable thing Donald Trump has ever said or done; no reason this one should be the straw that broke the camels back.
That implies there are actual Trump supporters, as opposed to low information GOP voters who kinda like a guy who is being flamboyant in the media. I definitely think Trump's support is inflated, and will dissipate quickly even IF Trump stays and leads til the Iowa caucuses.