No, the right side hitter is not considered a weak hitter... the right side is just considered your weak side, left side refered to as the strong side.
It's referred to as the weak side because it's often harder for right handed players to hit from the right side, also, thats your setters position...right side. Typically most people (not all but MOST) have a harder time hitting from teh right side of the ccourt....(Less then 15% for the population is left handed.) Since lefties are "rare" so to speak, and when you hit a volleyball you tend to swing across your body, left side is easier and more effective. The right side hitter is also called opposite, because they are opposite to the setter.
If you have an awesome hitter that hits on the right side and is right handed, and you moved her to the left side she will likely hit harder and stronger on the left... (unless she's trained on the right side for a while)
In all actuality the right side is just called the weak side because the world is predominently right handed...but by no means does that mean you have a weak hitter on the right.
Just like if you had a team of nothing but left handers...your left side would be considered your weak side...