Typically commentators have their own agenda, and they pick materials to support their arguments. Good commentators don't hard sell their agenda, and they do fact checking. Bad commentators cherry pick supporting materials, and they don't do fact checking.
方玄昌 had his agenda and his wanted to push it. That is fine, however, cherry picking "facts" didn't make him any better than those he accused for spreading rumors.
1997年，美国要发射“卡西尼”航天器用于探测土星，
因其工作电力来自于一个放射性同位素引擎，一些极端环保主义者以“万一发射
失败，放射性物质将造成污染”为由反对、阻挠航天器发射。反对者是如此执着，
乃至于让美国宇航局几次更改发射日期，最后是在“偷偷摸摸”的状况下发射
（国家天文台李竞老先生的描述），发射成功后才告诉公众。在今天中国的许多
公知及媒体人看来，美国宇航局的这一行为恐怕有悖于“知情同意”原则，但美
国普通公众并未对此提出异议，相反，很多人谴责那些极端环保主义者。
I don't know of 方玄昌's background, and I don't expect he knew anything about space mission. However, he should at least did his homework and fact check his source. Since Cassini-Huygens needs gravitational assist orbit transfer to fly out of the Solar system, the launch window is pretty restricted. If Cassini-Huygens missed the window, it had to wait for a year to launch. NASA did not change the launch date because of protested, NASA changed the date because of high wind and other technical reasons but within the window. And NASA definitely did not "最后是在“偷偷摸摸”的状况下发射，发射成功后才告诉公众" The launch was well publicized.
Here is the link to CNN News articles about Cassini-Hyugens launch
http://www.cnn.com/TECH/9710/13/cassini.delay/ on Oct 13, Cassini was launched on Oct 15. Why 谣言总占上风? 方玄昌 had personally demonstrated to us.