It's not a lateral move because
1. the Nets pick becomes more valuable
2. Young > Amir
Your claim that Young is better than Amir is highly debatable.
Please tell me what Thaddeus Young can do that Amir cannot? What actual strategic advantage does this team gain by replacing Johnson with Young?
Defense? No.
Ball movement? No.
Floor spacing? No.
Rebounding? No.
Fnishing around the basket? No.
Toughness? No.
Rim protection? No.
Intangibles? No - Amir has a league wide reputation for his intangible values.
Oh and before you say scoring, take a look at Young's career history - he's only averaged >17 PPG once in his 9 year career, despite the fact that he's always been one of the top 2 or 3 offensive options on the teams he has played on.
Don't get me wrong Young is a nice player, but to have great value in this league you need to either do one or two things at an elite level, or else you need to do
everything very well. Young falls in neither of those two categories. He does one or two things very well (but not elite), and is mediocre-to-average at everything else. To make matters worse he is also a tweener in the most pure definition of the term, since his body and game aren't optimally suited to either the SF or PF spot.
Young is basically a skinnier, more athletic Brandon Bass without the elite jumper.
If you ask me Amir Johnson has more value because even though he also is not elite at any one thing, he does absolutely everything well.