I'm going to forcefully lay down the law to a friend that he needs to either do something or quit whining.
Why do you want to tell him that?
I think he should be more responsible for his action and decisions.
If your friend's behavior is frustrating to you, you should voice your concerns is a calm, respectful way. If you want him to resolve his problems more decisively, perhaps it would be helpful to give him tips for thinking through his decision and making a choice.
He doesn't respect me and my opinions. I'm going to take a stand against this right now.
I understand that you are impatient with your friend's constant complaining, but being forceful and authoritative with him is not respectful of him either. Have some compassion for your friend and support him instead of criticizing him.