Well...for currencies besides Dash the risk is somewhat reduced by the fact that the effects of such a backdoor can immediately be observed, whereas with Dash the "spork" model means that an exploit can be hidden away and only activated at a later stage, or the network can be remotely forked by anyone who holds the spork key.
Wrong.
The spork is merely a secondary lever, not a magical "activate terrible code"-button. A malicious Monero developer for example could implement "underhanded code" into your official GUI-wallet release (you know, in 2045 or so when it's finished) with the simple instruction of having it activate when certain conditions are met, like a date, a block height, a difficulty level, even a certain transaction amount or a combination of any of these conditions. Heck, for all I care he could program his own spork as underhanded code into your release and create the same exact scenario you just tried to reduce onto DASH.
As you can see, your central argument has been easily refuted, making Dash just as vulnerable to that method as any other crypto. Not more, as you tried to construct. Nice try though.