Philip Morris is going on the offensive against some of the charges of three former scientists revealed early this week by the U.S. Food & Drug Administration. Page ads headlined "What does Philip Morris have to say about the allegation of `nicotine manipulation?' Plenty," break Friday in national newspapers and in newspapers in the top 10 U.S. markets. Young & Rubicam, New York, handles Philip Morris corporate advertising. Philip Morris chairman Geoffrey Bible, in a memo to employees yesterday, said much of what the ex-employees had to say is not new or is wrong.