As long as you use very fine grit sand paper used for wet sanding it is perfectly safe( I use 1500 and then 2000). Its only plastic. Just dont use a heavy grit that could create gashes in the finish. I have done this several times and on several high end cars with not a single problem.

You can do google searches or even watch videos on youtube of this same procedure.. All those rubbing compounds and creams dont work for beans if the lens has extensive UV damage. You have to get passed those damaged outer layers.