In general seems like Q posts his statements as questions. To remain within some legal boundaries, and to honor the Socratic method and encourage the "think for yourself" approach. So possibly the key to understanding this one is to think about how both statements are true.
My take so far is that satan (literally, "the enemy") exists, and his thought process exists in evil people.
Another interpretation is that some people worship (give everything for, and live their lives according to) the principles satan stands for. Principles like power-hungry rebellion, worldly riches at any cost, hate-filled control over others, and no higher authority than your own desires. So they worship satan in that sense, even if they don't literally do occult rituals where they chant oaths in dark rooms with pentagrams. Which would be many people's image of what "worshiping satan" means.