I'm not sure whether Roenicke's approach is a good idea or not, but if it's a bad idea, it's not for the reason F.P. gave--that this isn't how it's been done for 100 years, ergo it must be wrong.
Here are a couple facts Bob and F.P. either don't know or ignored. First, the Brewers are second in the NL in ERA. That's with Zack Greinke on the DL and a back-end of the rotation that no one wil confuse with the Phillies. And as Bob himself noted, no team in baseball has improved their team ERA from last year to this year more than the Brewers have.
Now, it's too early in the season to read too much into those numbers, though it's more valid than Bob and F.P. junking the idea based on a 1 AB sample--Mike Morse's lucky hit against the shift in the second inning. But at the very least we can say that so far Roenicke's strategy hasn't killed his team yet.
Here's the more important thing to keep in mind. The Brewers have a horrible fielding infield, with career UZR/150s of -6.7 (Fielder), -8.3 (Betancourt), -7.7 (McGehee), and -6.4 (Weeks). I almost spit out my drink when F.P. claimed that Rickie Weeks has "fantastic range."
Knowing that this infield is going to have massive gaps regardless of where he positions his players, why not try to aggressively position players where the spray charts say batters are most likely to hit the ball?
I'm most skeptical of the shift when there are runners on base, which did in fact come into play in both the 2nd inning, when the shift cost the Brewers a possible inning-ending DP, and in the 10th, when Werth was able to score easily on an infield grounder because no one had been holding him on 3rd.
But I like to see managers challenging conventional wisdom and experimenting with different ways to hide their players' weaknesses. I'll be interested in seeing how the Brewers' fielding metrics stack up as the season moves along, and I hope Roenicke doesn't back off when he faces the inevitable hindsight criticism every time a seeing-eye grounder sneaks through.