I do not see declare war in the list of my attack options in primary server.

I am in GDI but I have not read anything about GDI not allowing it.

How can I declare war so I can Crush this guy that needs to be destroyed?? :)

You cannot get the +10% military strength from declaring war in primary. You'll have to survive without it.

But is there still a declare war? I just need it to attack a guy that I can not due to gdi

You cannot get around GDI in primary. Either you're allowed to attack the guy with harmful spy ops and special attacks or you are not. Declaring war cannot change that. Declaring war cannot get you around humanitarians, if humanitarians protect him, then declaring war will not change that.

You need to get within 4x of his networth to just attack him with SS/PS, and you need him to attack you back twice before you can do any harmful spy ops or special attacks (although stealing cash, tech, and food is allowed even against people that have never hit you)