Why would he be foolish to say, "I neither illegally acquired prescription painkillers nor asked or allowed anyone to do so for me"?
I've sat out these discussions but now feel that I must comment to those asking why Rush never gave a flat out denial:
A blanket "I never" is the worst possible thing that anyone can say, uness it is specific to one and only one thing, i.e. - I never had sex with that woman, Ms Lewiski. A statement like that does not deny, sex with that other woman, only the subject of the denial.
Now, let's look further into this. Assume that Rush was out of a certain pill (use Claritin as an example since it was once regulated). Rush has a sinus problem one day and the cleaning lady gives him a Claritin. Two years later, after this "revelation", he makes the mistake of a blanket "I never obtained prescriptiond drugs from ....
When the Claritin issue comes up, then it's, well I never obtained any such and such from .... until the media now can say Rush denail proven wrong, he did obtain prescription medications from .....
Better to say nothing at all then make a statement that may be false, even if it's over one pill.
That's my opinion, but thten again I'm not a lawyer, only an interested bystander.