I didn't miss the point, I just don't believe it.
That's not what your post implied. Well, the first part anyway.
As for ulterior motives, I have no doubt there are some. But his speech was about him fighting for a flower poetically
. The actual speech was that they were fighting them because they stole their home from them, and that maybe one day if they completely destroy them, they'll be able to return to their home. Until that day arrives, they're aiding all the other worlds and civilizations they come across in the hopes that they won't have to go through what the Volm went through.
And despite knowing that there is likely some kind of ulterior motive, there's nothing very suspect about that reasoning aside from one's own paranoia. It's one we, ourselves, could likely make if we were in the Volm's position.
ETA - President Hathaway asked why the Volm were fighting the Espheni, but Cochise merely answered with the reason he was fighting. Basically sidestepping the question by giving his personal motive, but not his people's motive.
No, he was speaking for his people as a whole, using the flower as his personal
motivation in order to give the story more oomph.