I have had a couple of these, you can ignore and save anyway, putting a note in the bio to explain (if you think it is necessary to justify yourself) and just to explain your reasoning to anyone else who might come along and try to edit. The red banner is a slight pain in those circumstances as it keeps popping up every time you edit, but you are not obliged to change fact to satisfy the red banner, it is just there to help stop us making major errors and century typos, not tell us what circumstances are acceptable. Some of my family were baptised in their teens, so it would have been necessary for me to do the above if the father was already dead, in the interests of accuracy. Accuracy should always come before satisfying the system, in my opinion.