Alex has a lot of trouble with the word "no". Since he is emotionally much closer to a toddler than a teenager, the immediate crushing of his impulses tends to evoke a tantrum no matter what future delights have been promised. (Like: no we can't go see the OLG sign right now because we're going to get ice cream.)
Yesterday, we had a big tantrum over what he wanted for dinner (A&W). He'd been told that morning that we weren't having A&W. He'd been told that afternoon. He'd been told repeatedly during our trip to the grocery store to pick up hamburgers to make (my vain attempt at a compromise). As we walked back to the car, the endless cycle of "A&W!" "No." finally reached a breaking point and I told him to stop asking.
His response was to turn around and shove Nathan into the pavement.
This is not an uncommon cycle with us. Alex gets fixated on something he can't have (last time it was he wanted to go back to Disney that afternoon) and starts an endless "Now? Can I have it now? What about now? Now? How about now?" that is substantially less funny than the comedy routine. We've tried ignoring it but he will increase both volume and proximity until he is shouting less than an inch away from our faces.
When he finally grasps that our refusal is absolute and not just a matter of timing, then he reacts violently.
I've had well-meaning suggestions that I should just avoid saying no. If Alex asks for something he can't have, I should offer him something else. Ignore the request and focus on something he can have.
But 'no' is a part of life. We all have to deal with it. Pretending it's an option or a gateway to better things is a disservice both to Alex and every single person he will ever have to deal with.