It surprises me (although it probably shouldn't) that this topic generates such controversy here, almost as do religion and Israel/Palestine. BTW, these folks are pretty good friends of ours, I like them just fine, and we've had the BFF staying at our house for weeks when her school schedule required her to be in town.

"Thank you very much for the nice invitation. I would love your company at this special time. The dog makes me uncomfortable. Is there some way you can keep it away from me?" saulgoldie

As should be apparent from my OP, that is exactly what I said.

"it is incredibly rude of you to insist that the hosts meet your demands." - HiLo

Is it "incredibly rude" just to ask the question? See above.

"your statement that the dog has shown aggressive behavior is not very convincing." - crazy little woman

You weren't there, so what do you base that on? The dog practically went Cujo on me. It lunged at me, and the BFF's husband had trouble holding it back. I found the experience quite disturbing.