I don't know what language has to do with it.
Walking upright does give you the advantage of free use of your arms for something other than travel, including the use of tools or weapons.
But self-defense is pretty instinctive, regardless of how you move.
Apes, hominids alone and empty handed are no match for lions or other large African predators. Chimps have been seen using branches to scare away leopards which are solitary predators. They have to do it in large numbers. But the trees are never far away. To deal with packs or prides of large predators away from trees, hominids had to organize. They had to communicate. And, they had to have weapons more reliable than rustling leafy branches. Otherwise, they would have been eaten. Early hominids would have needed to communicate more than screeching and howling. They would have had to have a rudimentary nown-verb way to signal an effective defense against a pack or pride of predators. They would also have had some sort of weapons - clubs, long pointed sticks to inflict pain in predators.
Bear in mind Chimps can use tools. They can organize. They can even carry out warfare with other chmip colonies. But they can't walk very well because they need to be able to climb trees to escape predators because they can't mount a well coordinated attack or defense. Bear in mind we are talking about a creature more intelligent than a Chimp.
Bipedalism did not precede tools and language. There is no evolutionary means for it to develop if all hominids have is to be eaten up on the plains. Tools and language preceded bipedalism.