Read it again. The law prevents predatory pricing which is what Comcast is engaging in by charging one price to one franchise population and a much higher price to another.
quote:
...and where the effect of such discrimination may be substantially to lessen competition
Which is why Comcast is doing it. And notice that the law says, MAY BE...Google doesn't have to be significantly harmed or run out of business as the point of the law is to prevent the harm in the first place.
If Comcast wants to compete it should be on the merits of the product, not by using revenues from other franchises to subsidize lower prices in this one.