"The urge of sex has been grossly misunderstood, slandered, and burlesqued by the ignorant and the evil minded, for so long that the very word sex is seldom used in polite society. Men and women who are known to be blessed - yes, BLESSED - with highly sexed natures, are usually looked upon as being people who will bear watching. Instead of being called blessed, they are usually called cursed."
Source: Think and Grow Rich (book by Napoleon Hill)
What does 'people who will bear watching' mean in this context?