I don't think he was saying that he didn't care about a cabin fire. I think his concern is a less experienced FA calling the cockpit at 100kts for something which may turn out to be unimportant.
That being said, most briefings I've seen/done here will tell the FA to call whenever, sterile or not. I think most understand this to mean while we're airborne. The OP does raise an interesting point though.
Personally, I've only had one FA call below 10k, and that was a medical issue. Perhaps they're taught not to call between the start of the TO roll and gear up, unless it's a dire situation?
OP, remember that the FA may indeed call near V1. It'll then be your decision to answer. Regardless of the outcome, I doubt many people would criticize you for not answering.