He wasn't that big, and that's still not saying much, given also it's a disney toon for one and Herc was pushin the guy up. That's more strength than durability. Also it's quite a fact that bricks are in general more durable against blunt force than against edged attacks. Hulk can toss shit into orbit but still get slashed by swords'n crap. This' no different. Guts has several advantages over Herc, including the fact he's outside the fate/destiny of the universe and the laws of Causality.