Of course he won't take questions, he doesn't want people talking about how he's a scam artist.

His cloud mining scam started as a textbook Ponzi, which naturally falls apart when there's not enough new money coming in to pay the earlier investors. 

But what if everyone kept their money in the Ponzi and didn't ask for payouts?  Then it wouldn't have to fall apart as soon. 

So how could you convince people to keep their money tied up for even longer?  Switch them over to something else - Hashcoins and Paycoins.  Then, since you're printing your own money, you can pay them as much as they want with this new money.  Because it's worthless.  GAW keeps all the dollars and bitcoins, and gives out fake money in exchange.

But what if you could convince people to keep even their fake Paycoins tied up longer?  Then the Ponzi scheme might survive a few more months!  At this point in the game, the only people left are completely brainwashed or just stupid.  Or maybe they just keep hoping for the best, since all their money is in it and they don't want to admit that they got scammed.  So when you tell them to leave their Paycoins in a "cloud staking wallet", which makes no sense, they still agree.  And they pay more money.  They're along for the ride, and you're in control.

So when you go to the Bitcoin conference, you don't want to suddenly start answering questions from people who aren't along for the ride.  They're not under your control, and you've gotten used to surrounding yourself with followers.  Besides, why should you answer to anyone who isn't giving you their money?  The only ones you care about are the ones who believe whatever you say.  That's your target demographic, not people who need questions answered.