The passage explains that flags of size 20-by-38-foot is normally hoisted on national holidays and smaller flags are hoisted on any time is not correct. The size of flag shouldn't restrict patriotic expression.
The statement which weakens the argument made in the passage. Lets analyze:
(A) Many people find the garrison flags’ size to be distracting and ill suited to neighborhood aesthetics.
This statement doesn't question patriotism however it restricts hoisting flags. Eliminate
(B) The businesses that are flying garrison flags do so primarily to attract customers.
This weakens the argument as the flags are being hoisted primarily for business not for patriotism.
(C) The raising and lowering of different-sized flags on the correct days of the year is a laborious and time-consuming procedure.
This doesn't weaken the argument that flags shouldn't restrict patriotism. Eliminate.
(D) The regulations that govern the correct display of the nation’s flags are part of an old and time-honored tradition.
Factual information. Eliminate
(E) The symbolic significance of a flag’s size is not generally understood by most of the customers patronizing these businesses.
Out of context. Eliminate.
Correct answer is B.