If a person intentionally and repeatedly inflicts harm on other sentient beings, that person cannot rightfully call themselves a Buddhist, let alone a monk.
You make some very sound and interesting points. People opposed to Buddhism (or religion in general) will often attempt to counter this claim by invoking the "No true Scotsman" idea which was popularised by the philosopher Anthony Flew: http://en.wikipedia.org/wiki/No_true_Scotsman
Typically, the argument goes like this;
Person A: "Buddhism is just another violent religion that causes trouble in the world. Look at what these monks are doing!
Person B: "But if they are doing that, then they are not Buddhists
Person A: "That's the No True Scotsman fallacy, which is no defence. If they call themselves Buddhists, then they are Buddhists. Look, they are even in robes, and live in a monastery
Person B: "But if they are not keeping even the most basic of precepts, then they cannot be counted as Buddhists
Person A: "Now you are just trying to pick and choose criteria which are favourable to you, to excuse your violent religion...etc...etc..."
This leads to an impasse, with both sides trying to claim owndership of the term "Buddhist". (There is a lot of weight on the side of those who are in favour of self-assignation to a particular group as being the defining characteristic of that group, which is a consequence of a western liberal tendency to allow people to speak for themselves, and call themselves what they will.) But there are at least two ways out of this impasse. One is - as you have done - to point out the exception outlined in Rationalwiki above:
Broadly speaking, the fallacy does not apply if there is a clear and well-understood definition of what membership in a group requires and it is that definition which is broken (e.g., "no honest man would lie like that!", "no Christian would worship Satan!" and so on).
Other examples would be the "vegetarian" who is OK about eating chicken and fish, and will eat meat if refusing it would offend their host, etc. They are indeed "no true vegetarian", regardless of what they call themselves, and if we allow that some things can
over-ride self-definitions, then we can try to convince our opponent that the monks in question are "no true Buddhists". It's difficult, however, when rioters and killers are wearing saffron robes and are attempting to justify their actions in terms of accepted Dhamma!
Another approach is to be aware that the term "Buddhist" is merely a label or designation, which is applied to certain individuals according to socially-defined criteria. In reality, there are no "Buddhists". The Buddha himself had followers, but he didn't reify the label into anything. We just label certain people as Buddhists, and the dispute then becomes about which criteria are more important. I have no difficulty in saying "Yes, these particular 'Buddhists' - whatever that means - are killing and rioting. But they are not acting in accordance with the Dhamma". That, for me, would be the most important point.