There is a misunderstanding here. The President should employ a team of lawyers and prepare a legal defense. He should also prepare a "public face" for this and be coached by communications advisors and the like-- and he should follow their advice for a change. What seems strange is what some Trump supporters are doing (and they might be acting without direction from Trump) attacking Comey personally, and running TV commercials and newspaper adds to do this-- that is unusual. If Trump is behind it, that would be significant because it would look like he is trying to attack personally the former Director of the FBI who is testifying on things that directly impact Trump. Legal defense OK-- personal attack is not.