I'd suggest that the 'what if' consideration is infinitely preferable to the 'I didn't think of that!' realisation. I.e. "I didn't stop to think 'what if sh*t doesn't taste very good' and now I've chucked the butter out. Looks like I'll be eating sh*t sandwiches from now on".....Using "What if ... ?" is not a valid argument. Sorry.
Whenever I used the word "if" during a discussion, my Dad (not the most eloquent of men) used to remind me, "IF? If sh*t were butter we'd all be spreading it on our toast."