1) No they don't. They generally constantly try to highlight the hazard, not downplay it. Do you ever read actual science journals? Watch Science channel documentaries? Of course, if any natural scientist DOES highlight a given hazard, then people on FR savagely attack them for "just trying to get more money."
What they DO downplay is the hazard of specific asteroids with well-calculated orbits that miss the Earth, when kooknutter sites claim otherwise.
2) Stop getting your science knowledge from kook websites and bad movies. Of the many potential methods to try to divert an incoming asteroid, nuking them is one of the dumber ones.
You seen this?
Dramatic CCTV: Meteorite blast wave blows out doors, windows in Russia.
Caught on video, watch what the shock wave does to this door and office.
http://www.youtube.com/watch?feature=player_embedded&v=1kvHl5Qcnzc
Experience shows that astronomers try to be honest about any 'hazard'.
It is the media and the government who control what is revealed to the public.
Of note is that governments have built NEAR (telescopes that watch for Near Earth Asteroids, comets, etc) Stations all over the world.
The problem is that fast rocks with no headlights are hard to see, and there are an almost limitless amount of 'tracks' they can take.
Besides, most of the NEAR meteor info is available to the public rite-cheer.
Recent & Upcoming Earth-asteroid encounters: At bottom of page.