The point of public political hearings is PR. To help legislators show voters that they care about whatever crisis is top of news. Information seeking and legislation writing happens in closed door negotiations with lobbyists and lawyers.
If Senator Graham genuinely wanted to know about Facebook's competition, there would be legions of staffers and thousands of pages of reports on it. If Senator Graham were genuinely not sure what to do about Facebook, there are exceptionally well-informed people in his office to summarize the landscape, the propsals, the pros and cons, and to debate the finer points, who are deeply familiar with everything AEI/Heritage/Cato/Brookings have to say about it, etc. because that's their full-time job.
By the time you hear a pointed question in the committee hearing room or a speech in a floor "debate" from a Senator, they've been over it with staff, decided on a position, and calculated the optimal move to present to the cameras. That you enjoy or agree with the thrust of this particular show has no bearing on the theatricality of committee hearings as a tactic. They wouldn't do it if no one enjoyed it.
It's not that politicians don't debate things in good faith. It's that they do it with and through staff (who are more like the people you find in high school debate than televised election debate), behind closed doors, and not on the floor.