GWB had a plan for future manned exploration. GWB killed the shuttle, but he had a replacement, 6 years in development and Obama scrapped all that research and development. Private firms for ISS is fine, but that's not space exploration. That's doing something that NASA has done since the 60's. Obama put out this vague plan with no real focus about people on Mars and asteroids. A mission to Mars will require almost year stay on the planet, that is never going to happen without testing of equipment, and that equipment will be tested on the Moon. Obama used the stupid excuse that "we've already been there".
Obama didn't kill the shuttle, but he did kill NASA's manned space program for at least the next decade.