While your claims are reasonable, I must disagree; First of all, an educated guess, even if it's only off the barest fragments of foundation, is going to be more accurate than nothing. Secondly, we can make relatively reasonable predictions based off of physical factors. Pick up a sci-fi book; most of the better authors actually try and work some logic and reasoning into their aliens.
As for 'discussing what they'd behave like', that's... well, in a bastardized version, as-applied-to-this-subject, it's the scientific method; Take a basis, (In this case, that aliens are weeaboo for humans, as laid out in OP,), then attempt to explain what affect this would have to the best of our capabilities. (Obviously not very good- we have enough trouble with our own societies.) But it's the best thing to go off of, so we state our thoughts, our predictions, and our reasoning behind them. Then offer them up for peer review.
Now, you're probably right that they have no value beyond just an imagination exercise, but hell, that's value enough in it's own right.