You have a point in one way, but the other way is equally true. These individual nationalists are using Buddhist doctrine as much as the pacifists are. I think I'd also be cautious to say that these are exceptions to the rule. Buddhism still propagates the idea of the 'true way' in it's rejection of Brahmanism... and that is exactly the same mentality as Christianity or Islam. In the Jatakas, the various stories of Buddha's past lives, Brahmins are routinely patronized and viewed as silly. Likewise, the justifications
The biggest issue I have with your argument, although you have a good argument, is that I disagree that Gautama is central to the religion. He is the historic Buddha yes, and the varied monk-lineages trace their origins back to him... but for the majority of Buddhists before and even during the colonial period, his words were not central to the religion. You're approaching it from Buddha's words which is fair to do, but if approached from interpretations of the Three jewels, then war in the name of Buddhism (whether supposedly defending the Sangha or the Dhamma) is perfectly justifiable from a religious perspective. Likewise, non-violence is not the core of Buddhism... nirvana is, and how one reaches Nirvana can be from non-violence or it can be through mass merit making. If it were just a few handful of nationalists causing mayhem then I could agree with you, but this justification has been used in warfare foir over 2000 years.
In my view also, religion in general cannot be condensed down to texts because those texts are products of the certain time and place they were constructed. The religion is multifacted and although it's nice to look in the Bible to look at teachings and beliefs... remember, beliefs are often constructed from interpretation of stories. The Bible does not explicitly say 'velieve in this' the majority of the time. And, text based religion is really a model of western religions that was imposed onto the academic study of other religions during the colonial period.