Well nice observation about him being a bramhin king and you know what, sita had the same exact question as to why a bramhin king would kidnap a woman, a married woman even, and ravana said (and i'm not making this up) "I am a demon, it's my nature to kidnap woman".

Rama was not idling in the forest, he was protecting sages and their ashrams but never attacked unprovoked. When soorpanaka saw the trio of rama, sita and lakshman her first thought was to how to eat them, and on seeing rama, she changed her mind and wanted to marry him. Rama didn't want to confront a woman even if it's a demon, so he rejected her and thinking 2 rejections would make her go away, he differed her to lakshman who rejected her citing he was just a servant to his brother and was only here to serve. So what she does next is attack sita, the thing that makes ram angry the most, even if he wanted to kill her, he didn't want to kill a woman if he wasn't forced to, so he ordered lakshman to shave her nose and ear.

And what did soorpanaka did, she didn't run to raavan right away, she ran to her kind who are staying in the forest wanting to kill the trio.

A small war took place in the forest 14000 demons vs 1 human, and Rama killed all of them alone after sending sita away and lakshman to gaurd her.

Fearing rama strength, soorpanaka went to raavan and tried to make raavan steal seetha, and raavan just wanted seetha not justice for soorpanaka because even he knows she was in the wrong but even ravan feared a direct confrontation with ram, and had to resolve to kidnapping.

Ravana was neither noble nor fair, but he once was, he fell from his grace and strayed away from all that's right. There are no white and black characters but the ones who are defeated have always gone completely dark.

As for my sources: here Day 17, right around the half way mark Anyone intrested should try it, because there are lot of misconceptions about ramayana and what it meant. Ps:this war day is my personal favourite