Don't let them attack. Long pips can only attack against backspin, or sometimes against a short and weak topspin or no-spin ball. So keep the ball deep, and usually either put no spin on the ball (and so get a no spin ball back) or give topspin (and so usually get a slower backspin ball return).
Take a step off the table, and return with a topspin drive of some sort. By backing off the table, you have time to react. By putting topspin on the ball, the ball arcs onto the table, and stops the long-pips player from attacking with the long pips again.
Stay at the table, open your racket, and be willing to lose a number of points as you get used to this.
Play against players who attack with long pips in practice as often as possible until you get used to it.