If Obama proposed Romney's budget as his own he would have been torn a new one from fiscal conservatives screaming from the high heavens about the biggest tax grab on the rich in our nations history, about redistribution, class warfare, and mostly how it doesn't even get prom point A to point B, "there is no free lunch" lecture.
Obama loves shooting down Romney's budget while neglecting the fact he hasn't come close to passing one in four years. Romney should have made a bigger deal of the blunder with Russia, half of the country probably didn't understand it.
Romney is promising a revenue neutral budget that lowers taxes 20% across the board and does so by limiting deductions, but not the popular ones that people like. Somehow this 500b annual cut in taxes will be paid for by who? magic gnomes? if the rich are paying for it (and they can't because there doesn't enough enough deductions to begin with) then it's a massive tax increase on them. Socialism!
It deserves to be mocked and ridiculed because when asked how he is going to pay for it he can't cite specifics and just says to "throw out a number" on a deduction cap (17, now its 25, maybe tomorrow it will be -3, who knows).
I don't think Obama's plan is great by any means, but by all reasonable accounts it's plausible that it can pass congress, and it's actually in line with math.