I'd agree... the 55-250 will come in handy for sports or at the zoo... It's a good lens for the money.
Well, what that person shouldn't do is sell that lens to get a 70-300mm lens, Canon or Tamron variety. That "upgrade" would accomplish nothing as the range doesn't fit well with most standard zoom APS-C lenses and image quality isn't any better than the 55-250mm. Only thing is the build quality will improve, but at the cost of size and weight.