He never said he was too fast for him I don't believe, he simply said he was fast :lolLike who exactly? Cause there is either something you are misinterpreting or something that is easily explainable.
You don't know where they started from so you can't say that this clash took place in the middle of their paths.
He was simply forced back, but you can see him blocking Hidan's attacks with his Kunai.
*Sigh* Kakashi right after this blocks Hidan's back attack and then they clash once more after that. So no, this feat is not comparable to Deidara and Sasuke at all. Deidara said Sasuke was too fast for him. Kakashi never had an issue handling Hidan's speed. Ever.
Either way he was forced back with no counter attack which means Hidan traversed that entire distance before Kakashi reacted, as if he could have reacted beforehand I see no reason why he wouldn't either evade or blitz Hidan himself, and at no point was Kakashi overwhelming Hidan with speed either.
As for the first point you can both Hidan and Asuma moved from their original spots (Hidan was in his sigil and it is clearly not there)
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These little spots of dust on the ground indicate where they land before they then clashed via dashes.