I would say no, that is not fairly representing the Christian worldview. A Christian can claim to know some general truth about God's will, without having to also claim to know every particular truth about God's will. I see no inconsistency here.
It's a basic category error to assume that because someone believes what God wants you to do with your whole life, that they also ought to believe what God wants you to do each and every minute.
An evangelist's ignorance of what God wants you to do in the next 5 minutes shouldn't dissuade them from trying to persuade you to accept Jesus as your Lord and Savior; nor should it dissuade you from hearing them out. Why? Because it's not their job nor their place to tell you to take a sip of coffee, or tell you that they believe God wants you to take a sip of coffee, or whatever. That's the cool thing about having freedom. Let's trade out the evangelist for say.... a salesperson offering you a special deal on a cruise, and they begin their pitch with "you need this vacation," and you quip back saying "oh yeah? well if you can't tell me whether or not to take a sip of my coffee RIGHT NOW, then you can't tell me I need the vacation you're trying to sell me. GOTCHA!!!!!"
A skeptic and Christian meet at a coffee shop. When he learns of the skeptic's skepticism, the Christian says "God wants you to accept the Lord Jesus".If the skeptic said "What does your god want me to do RIGHT NOW?", how could the Christian respond?Does God want me to ask you for a bible?Take another sip of coffee?Look out the window at the truck that just hit that telephone pole?If the Christian cannot seriously state what God's will is for the skeptic concerning the skeptics next action or thought, then why shouldn't the skeptic conclude that God doesn't want the skeptic to have the answer...thus morally justifying the skeptic to provide that answer for themselves?So that if the skeptic declines the salvation invitation, this is reasonably construed as god's fault for refusing to reveal his particular will?