Hmmm ... I think you need to take a good look in the mirror before saying someone else is "self-righteous".
self–righ·teous
having or showing a strong belief that your own actions, opinions, etc., are right and other people's are wrong
True. But it seems as if the situation here is binary. The people who use extra MBs to obtain more FP+s than their admission price entitles them to are either "right" or they are "wrong". So one of two things must be true:
A. Either the OP is "right" and the people who obtain additional FP+s are "wrong"; or
B. The OP is "wrong" and the people who obtain additional FP+s are "right".
And if this is the case, then only one side of this debate can be self-righteous. Either the OP is wrong, but thinks he is right, making him self-righteous; or the people who obtain additional FP+s are wrong, but think that they are right, making them self-righteous. Both sides of the argument cannot be self-righteous, because one side believes that they are right when really they aren't, and the other side believes that they are right, and in fact, they actually are. The former is self-righteous by definition and the latter are not. They are merely "right".
Example:
Joe insists that George Washington was the first president of the United States.
Fred insists that John Adams was the first president of the United States.
Both insist that the other is wrong.
Joe is not self-righteous. He is merely right.
So pick a side. The OP is only self-righteous if the people who use extra MBs to obtain additional FP+s beyond the three to which their admission fee entitles them are actually right in doing what they are doing. But if you believe that people who do this are actually wrong, then the OP cannot be, by definition, self-righteous. You might not appreciate the tone or the fact that they wrote the letter. But those things do not fit the definition of self-righteousness.