Would you explain the differences among journalists, columnist, reporter, blogger, etc. Of course we know activist and editorialists.
You ask why Bush doesn't pick up a megaphone and respond to Trump's taunts. It's because you, like the rest of the media, are giving Trump, and hardly any of the other candidates, most of the megaphone.
The media loves Trump because they are both irrelevant. Both are attention whores. Some of us like a few facts, unsensationalized, so we go to other sources who are actually journalists.