In table tennis, there are two general player types.  There are players who win most of their points by hitting strong shots; against these opponents, you need to stop their big guns.  Then, there are players who keep the ball on the table and win most of their points from YOUR errors.  Against these opponents, you need to eliminate mistakes, be selective, be consistent, and look for the right opportunity to dominate with your game.  The defensive chopper falls into the second category.  The defensive chopper might occasionally attack against a very easy ball, but he is looking to win about 9-10 points per game from your errors.  So what if you just pushed and pushed and pushed, would that be a good plan?  Well considering the fact that he specializes in pushing and chopping, you probably won’t outlast him.  So what should be your plan?  The plan is the keep the game simple, eliminate errors, and go for strong smashes and loops AT THE RIGHT TIME.  You can relax knowing that your opponent won’t hurt you.  You have plenty of time to work the point and play tactically!
 
 
Equipment
Before you begin the match, check his racket to see what type of rubber he is using.  Often choppers have inverted on the forehand and pips on the backhand, be sure to check if he is using long or short pips.  Long pips will give you more of your own spin back when you are looping and short pips will give more variation.
 
Serve
When serving against the chopper, I would recommend serving deep no spin serves with good placement variation.  Especially deep serves to the middle tend to be difficult to return with quality.  Also, try serving short topspin to the forehand.  If the chops pushes it, it often comes back high.  If the chopper flips it, then you can immediately begin with a quick attack before he has time to get into position.
 
Receive
Get the ball on the table.  Dude, this guy doesn’t attack.  There is no reason to try to rip the heavy backspin serve sharp to his wide backhand.  Just make a simple loop or push with plenty of arc and begin the rally.  REMEMBER, his is counting on YOUR errors in order to win.
 
Rallies
Again, be consistent in the rallies mixing up pushes and loops.  Hopefully, within the first 1-5 balls, he will chop high enough for you to hit a power shot.  If he is good at keeping it low, then also consider pushing and looping higher. 
 
 
Placement
Playing to the middle and using the angles are often good.  If the chops and pushes are coming deep to you, then attacking the middle is usually better.  If you get a short one, then go for a sharp angle push followed by a sharp angle attack the other direction.
 
 
Mindset
You mindset needs to be shifted slightly.  I know that you have programmed yourself to loop all the long balls and to loop low and deep with decent power.  However, if you begin losing then you must change your mindset.  Slow down about 5000 rpms, calm down, take some deep breaths, and remind yourself to work the point longer.
 
Fatigue
During the long matches, fatigue might become an issue.  Remember that you as the offensive player will likely tire out before the chopper.  With this in mind, try to take at least 8-10 seconds between points.  Even if you are winning initially, try to resist the temptation to play the next point fast.  Think of the match as a marathon, not a sprint.
 
Practice
As with all the various types of opponents, making proper adjustments is important.  With a few minutes of pushing and controlled looping practice before the beginning of the match, you can physically and mentally be prepared to control the match against the chopper, work the point, and go for it at the right time!