Is it rude to use the search function?

I just made an F-list 2 days ago and I still don't really know what I'm doing. I was using the search function to find characters from the series I RP from, but hasn't messaged anyone yet. I saw in some of the kink lists, some people added that they will "not respond if found through the search."

Is it rude to find/contact people you find in the search?
And if so, how do people usually find characters to RP with?