I'm arguing "both", but mainly that we don't need those people who would misunderstand or misrepresent X-risk. People react against things they disagree with much more strongly than they react in favor of things they agree with. Consider 3 social movements:

1) a movement with 1000 reasonable-sounding people and 1 crazy sounding person.

2) a movement with 1000 reasonable-sounding people, 500 crazy sounding people

I'm arguing that movement 2 will grow more slowly than 1, and will never become anywhere near as large. This is because new members will be very strongly turned off by seeing a movement that looks 1/3 crazy, even if they are slightly attracted to the non-crazy bits. If I wrote a script that inserted random YouTube-quality comments into LessWrong, you would get the strong impression that the community had slid into the gutter, and many people would probably leave, despite having precisely as many interesting and thoughtful comments as before. The crazier a movement looks on the surface, the harder it will be for academics to be taken seriously by their colleagues, and the fewer academics will be willing to risk their reputation by advocating or publishing on that topic.

As for titles, you are probably right that most people will forget them immediately, and any impressions they form would be negligible.

The search terms are mostly biological names for various extinction events throughout history, such as the one that killed the dinosaurs. I basically just skimmed through Wikipedia for obscure technical terms related to extinction.