A term for the object of insincere justification

Your "smokescreen" is quite apt and easily understood in context.

If you're looking for another or different term, there is "pretext", or, more colorfully, a "stalking horse", defined by Oxford Dictionaries Online as:

Stalking horse, from a screen traditionally made in the shape of a horse behind which a hunter can stay concealed when stalking prey.

A false pretext concealing someone's real intentions.

Other candidates include:

• Facade (and its synonyms charade, front, veneer, [false] show): an outward appearance that is maintained to conceal a less pleasant or creditable reality.
• Cover story
• Decoy

^{Aside: For the specific example you gave, see also NIMBY.}

^{Also, in the very specific context of one person using another person to conceal either his homosexuality, his infidelity, or his identity in dubious transactions, consider beard.}

It could be called a red herring

anything that diverts attention from a topic or line of inquiry [Collins]

It also could be called a diversion

A maneuver that draws the attention of an opponent away from a planned point of action, especially as part of military strategy. [American Heritage]