I sometimes do. Not always, but sometimes.
My point here would be that it is threated as a big deal in universe, and not just confirmation of Roger's words… All and all, either we go that the speach had very little effect on pirate community, which lessens the meaning of it, or that it actually had quite large effect, but also with negative side-effects. I personaly would go with the latter. Sooo... I dunno. You might be wrong, you might be right.
However, I would still say that it was ill considered of him to do, considering Fishman Island, and the problems caused by the original speach given by Roger. Seems a little bit unfair to Jimbei. But that's just my opinion.
I'm not sure if Whitebeard actually considered possible effects of his speech.
I'd think the speech could screw things up much more.
Any way aim of the speech was firstly and obviously to remind the Government and Marines, that their power is not secure, secondly, to give hope to those, who have at least some vague idea what One Piece is actually connected to, by asserting that it really exists. And that was major good thing.