At the begining of chapter 10 I believe that Ralph is justified in his fear. He is right ot be afraid. At the end of chapter 9 i think that raph realizes that the beast is not some creature it is their socioty. They are ruthless and they act on impulse. When simon was killed ralhp had a part in it. he didnt stop it he just let the beast kill. And because of this Ralph is afraid of the boys and een himself because he doesnt know what is going to happen next.
I agree with Morgan because Ralph has the right to be afraid. after all, he is only 12...ish. He is now realizing that the beast is becoming a part of each and everyone of the boys on he island. A prime example of this is, as Morgan said, when they all join in and kill Simon. Ralph had a part of it, too, which is why he is afraid. He is afraid of what he is becoming along with the other boys as well. No ones future is clear, and with these changes in character, their future remains even more loudy.
*i meant to say cloudy :)