It never ceases to amaze me how confident people are that the judge is an idiot despite knowing nothing about the case.
If this was a picture of him smiling with his airsoft weapon under a banner that says "12th annual airsoft picnic" then this case would be outrageous.
If this was a picture of him in in a balaclava holding a weapon with the caption, "I'm coming for you proddy bastards" then it would undoubtedly be of a "menacing character". Since he was being tried for menacing communication, not for posing a real threat, the fact the gun was a toy is irrelevant. If you can't tell its a toy, the picture is equally menacing.
I have no more idea than anyone else what the picture actually showed but since the magistrate was convinced, I think it's pretty likely we're talking about picture 2.