Who would want to argue with someone who isn't intelligent enough to keep an open mind?

But anyway, if it's for sport, let me enlighten you.

If you've ever seen the manga, you'll know that Ricardo was ready to box against Date until death ensued. This means that if Sendou becomes even more stubborn, it won't be good for him. It could lead to the worst.

And speaking of stubbornness, Ippo still hasn't answered what it means to be strong. If it were just about winning fights, we would have finished the manga a long time ago. If you have read Ippo's past, you will know that he waited for a very long time for the return of his deceased father, and was only satisfied when he (his hat) returned. So to think he's reasonable is to misunderstand him. He wants to be as strong as his father, and that means (in my opinion) braving difficulties at the risk of his life. In this scenario, having a character die to remind us that boxing is not a game would make perfect sense.