Yes, I accept that statement. Everybody recognizes design, and even purpose, every day. The sentences I read from you are obviously designed. When we ask why the centerfielder threw the baseball to third base instead of first, we acknowledge purpose by saying "fielder's choice". So by example, design and purpose are not unrecognizable in all cases.
It's curious to hear you arguing that Weinberg (and other scientists) must not dismiss design or purpose, on the grounds that they can't recognize it even if it's there. The whole logic behind the "Intelligent Design" fashion is that there exists some sort of objective litmus test by which design can be unambiguously detected. Either design is universally detectable or it isn't. If design is universally detectable, your in-principle complaint against Weinberg fails. If design is not universally detectable, "Intelligent Design" collapses as science.
(This argument does not cut both ways, as Weinberg does not say that design and purpose don't exist, just that the things in the natural universe don't require a design explanation.)
A scientist insisting that design is not evident is as great a stretch as saying it does, especially if one won't accept a criteria for recognizing design's existence.
Show us criteria that work, first. We're not saying that the design hypothesis is necessarily wrong, just that it's not necessary. But if it can be upgraded to testable someday, we can discuss it further.
So far as I know, only one "pro-design" person on FR has ever consented to play "general_re's" "Design Inference Game" in which he offers up several images of objects and asks the contestant to decide whether the item is the result of natural processes or "intelligent design," and provide the reasoning behind their choice.
The reality is despite much posturing and boasting, nobody seems to be able to come up with a very reliable mechanism by which to distinguish design from nature in the absence the context of the object under discussion. Mere "observation" doesn't seem to work very well.