Madara didn't fight the First Hokage it was his brother who died in his place.

[DepthCharge]

Madara's brother was dying anyways so Shishu went out and fought the 1st hokage and died.

 

[CheesyNaruto]

Madara's brother was dying anyways so Shishu went out and fought the 1st hokage and died.

Izuna is Madara's brother, Shisui was Itachi's best friend.
But I don't think he covered for him, the 1st hokage would have known he was his brother, why would he tell differently? And Izuna gave his eyes to Madara; Izuna fighting the 1st hokage with no eyes is a suicide mission.

 

[Typhon]

You realize Izuna had no eyes, right?

I think it would be pretty difficult for Hashirama to overlook the lack of eyes.......

 

[CheesyNaruto]

You realize Izuna had no eyes, right?

I think it would be pretty difficult for Hashirama to overlook the lack of eyes.......

Also adds to the unlikelihood of this theory.

 

[Honord Sage]

Madara did fight the First Hokage for control of the leaf and lost.

 

[tyran]

one coffin popping up seems to sprout all kinds of wild theories

 

[Honord Sage]

And they say Dead Men tell no teals.