First off, RONR perhaps should be more properly designated as your parliamentary authority rather than a fall back for various instances when your policy on meeting structure is lacking. As indicated above, the answer is no specific motion should have been required to start talking/discussing. But also as noted above, it appears your group should be using a standard order of business as opposed to an agenda, so you're from the start operating outside RONR, and trying to use RONR to fix issues caused by operating outside RONR might be fruitless. And that's fine, but as details later showed, apparently a majority of members wanted NOT to discuss the item. The will of the majority steers what happens. Again, even if the "forced" motion was improper or unnecessary, it doesn't appear anyone raised a point of order. And again, the majority wanted not to discuss the issue. It doesn't. But given the details you've described, it may be a moot point. Somewhere between approving the agenda and the "forced" motion, apparently the group changed its collective mind.