Good input and spot on to the original posters exact question.
Since it's been answered, might I pose another question that seemed like the elephant in the living room?
Why would you hunt with a rusty broadhead? Rust forms microscopic pits in the cutting edge, doesn't it?
We all speak about "scary sharp" heads to do the most damage. Why would you not work to remove ALL the rust to ensure a super sharp head?
If there is deep pitting, then you might not get it all, but I have to suppose that might be the basis of the poster's concern? Deep Pitting?
I've sharpened blades on knives and BH's that were badly pitted and while I can't get all the pitting out, I sure did on the cutting edge. Otherwise, that head is retired.
There has been excellent data provided to make the poster rest easy on the contamination aspect of a rusty anything causing tetanus infection, so I hope I'm not being insulting by focusing on the issue of a very clean, super sharp cutting edge to boot!