Its supposed to hurt you because automatically you get hurt because there is fire damage but you don't get the "fire"... iz so hard to say..
Don't include another bug in 1 bug... seems legit. LOL 1 Bug in a bug???
It may be your computer is lagging? Try restarting your computer/minecraft.
I don't know about the glitching part but you get fire damage technically even with fire resistance potion but the snow golem doesn't catch on "fire".