Again, you are ignoring the fact that Obi-Wan heard the plans of the C.I.S. leadership., which was to attack the Republic and overwhelm the Jedi, forcing the Senate to agree to any demands they make. Why is this not getting through?
Those 3 weren't the reason for the war. War was inevitable, because it's what Dooku and Sidious wanted. Obi-Wan reported this to the Council, the C.I.S. had no intentions of doing anything but attacking the Republic. This is why they gathered the Jedi to save Obi-Wan, Anakin, and Padme : War was inevitable, the C.I.S. was building a huge army for that purpose alone, the Jedi would save those 3 and buy time for the Clone Army to show up.
If you know an enemy is preparing for a massive attack, and you have the chance to strike first (while saving 3 incredibly important figures in galactic affairs), you're going to take it.
The Trade Federation provided most of the droids we see in Episode 2 (minus the Super Battle Droids). The Federation was banned from producing a droid army after Naboo. It was illegal.
Heh, you missed the entire backstory for Episode 2 I guess. The Republic tried negotiations for years, as soon as the C.I.S. was formed and announced their intentions to leave the Republic. But guess who the leader of the Republic was? A Sith Lord! Kind of, you know, manipulating events to push the galaxy into war.
It's been a while since I've seen the movies, so forgive me if I am forgetting some stuff like Republic negotiations with the CIS.
I know Obi-Wan directly overheard their plans for war and told the Council, but I don't think one man's word is sufficient charges along with one assassination attempt to go to war. If you are arguing from the strategic position, they made the right choice, but I still have doubts about the moral justifications; you even admit yourself that the Republic was led by a Sith Lord into this war whom you have argued are stirring up fights quite often. I'm not quite saying that the Jedi are at fault, but the Senate's actions are my concern.
Going back to the Trade Federation army, if their droid soldiers did not operate or were manufactured in systems belonging to the Republic I still think they had every right to build that army according to the measures of the governing powers of the CIS. The Republic should have warned them to cancel the construction of this army and begun to make war plans accordingly. On the other hand, building large armies is usually a problem for other nations such as in post WW1 Germany.