lord of the rings - Why didn't Aragorn and Glorfindel attack some of the Black Riders?

The answer to this is in the paragraph following the one containing the extract you quoted:

Glorfindel knew that a flood would come down, if the Riders tried to cross, and then he would have to deal with any that were left on his side of the river.

So Glorfindel knew that a trap had been prepared; the safest course of action was to drive the Nazgul into the trap, which was exactly what he did. The only need to attack any Nazgul would have arisen if any had escaped the trap, but until then there's no point in doing so, particularly as Aragorn - a mortal man (and recall Glorfindel's "not by the hand of man will he fall" prophecy) armed only with a broken sword - would have been especially vulnerable.

Killing Nazgul was not the objective here; the objective was to save Frodo and prevent the Nazgul from getting the Ring, and in order to do so they had to get Frodo to Rivendell as fast as possible. Everything in the actions they took worked towards that objective, so there was no need for any further action.