Situations where there is actually no choice are exceedingly rare, and the situation Lan was in was not one of them. He did not have to keep the ta'veren from the Shadow. He did not have to bring them to Baerlon or the Stag and Lion. There are any number of hypothetical situations in which the Stag and Lion could have avoided burning, but they didn't, so Lan justifies the burning by saying that the fact that it burnt proves that it was a worthwhile sacrifice.

Likewise, there are any number of reasons why waging war over a sandwich is stupid. The example was selected precisely for its stupidity. However, applying the same logic as Lan used in his situation, after the war has been waged, the fact that thousands died justifies the war for the sandwich. Even though there were any number of alternatives. The argument is expressed after the fact to justify whatever you just did as having a worthy cause, as demonstrated by the price that had to be paid to achieve it.

Actually, now that I think about it it's like the argument for the existence of gods based on martyrs. It goes 'nobody would have endured so much suffering for a god that wasn't real, therefore their god is real'.