The flaw in the logic of the o/p's question is more easily stated thus: the Earth has a given mass, and the tennis ball has a given mass, but each mass has a different value.
The Earth has planetary mass, according to which an object nearby in free fall will accelerate toward it at 30 ft per second per second. But the tennis ball has a mass of about 6 oz, so has a negligible acceleration upon an object nearby.
You cannot simply say that the acceleration of 30 ft/sec applies equally in both directions: simple logic will tell you that it applies only in one direction, since it is solely caused by the mass of the more massive body.
If the Earth was removed from the equation, no one would expect the mass of the tennis ball to exert any (non-trivial) acceleration upon any nearby object. So one could scarcely expect the Earth to be accelerated by the ball's (negligible) mass.
Furthermore, the logic offered by the o/p leaves out of account entirely the very obvious fact that inertia will hold the Earth in place. Unless the mass of the other object has a significant fraction of the Earth's mass, the inertia associated with the Earth's mass will prevent it from being accelerated in any direction by the presence of the other object.