This is the main flow in any story involving Ranma, and why

Takahashi 

kept piling stuff

on his back... cause the guy just won't stay down!  This, more

then 

anything else in my

opinion is what defines Ranma as a character, he won't give up!

(Though 

he does like a

challenge.)

Any story involving Nabiki actively confronting Ranma has to take

into 

account Ranma's nature. He would fight her every second of the day,

and 

wouldn't shrink from doing anything to win. 

Correction. Ranma would do whatever he could to best Nabiki, outside
the realm of martial arts. He would not attack her, nor would he have
someone else attack her. 

This has been done at least once or twice, and very IC in my

opinion

Ryouga has never been shown to be manipulated; he's been tricked by

Ranma several times, but has never been manipulated. Of course,

that is 

not to say he *couldn't* be manipulated, just that such a thing has

never happened. My point is that it probably wouldn't; people who

go by 

the the few dubbed anime episodes released by Viz and who don't 
understand basic elements of Japanese culture seem to view Ryouga

as 

this big bruiser type who is tricked by Bugs Bunny to walk off of a

plank.

If Bugs Bunny told Ryouga that walking off a plank would help him
defeat Ranma and/or win Akane, he'd do it. Ryouga is gullible.

Ryouga *has* been manipulated, BTW. Although Cologne's true motives
aren't certain (was she trying to get Ranma unhooked from Akane, or
trying to make Ranma a better martial artist, or both? We'll never
know for sure), she *did* manipulate Ryouga into learning the Bakusai
Tenketsu and fighting Ranma when she knew that the only thing the
technique would do is make Ryouga nigh-invulnerable to Ranma's
attacks. 

Ryouga sees himself as a warrior, steeped in the code of bushido.

Such 

characters, including Ranma and Kunou, amongst others, feel that

they 

are above normal people--they feel normal rules of politeness don't

apply to them. This view of himself is supported by an ego the size

of 

Wrong again...Ryouga is a very polite individual, except when it
comes to Ranma, and certain other martial artists. He's generally
polite to the Tendou family, to Ukyou, and even to Shampoo and
Cologne, although his relations with the latter two are a bit
strained. 

Mt. Fuji, so Ryouga would in all likelihood react badly to 

As far as this ego the size of Mt. Fuji...that only applies to Ranma
and Kunou. Ryouga is, by nature, a deeply depressed individual,
fueled by negative emotions. It is this that empowers his greatest
technique, Shishi Hokoudan. People whose lives are filled with
depression and despair don't have room for ego.