The idea that you have to meet some criterion, or have to experience something personally before you are allowed to argue for a position really irks me. Especially when that criteria is asymmetrical like this, it sounds like you're trying to get an excuse for ignoring the other side.

Anyway this criterion would probably backfire. (Edit: oh wait, you probably wouldn't see this as a backfire) Older people have lost many more child/partner/parents, and are probably more likely to be deathist. If deathism is a sour grapes/get hit over the head every day with a baseball bat and come to say good things about it response, those who have been hit over the head the most should say the most good things about it.