I did a quick search and could not find anything. My suggestion would be to ask Mike Reiss or someone else like him that does a weekly mailbag of questions. The reason I suggest Reiss is that he works for espn, and that organization probably has better resources than any other for researching those kind of statistics.
I'm assuming your co-workers are concluding that Brady gets favoritism based on (a) the often replayed penalties from the Ravens game in early 2009, (b) the relatively low number of sacks he has taken, and (c) they are jealous fans of other teams trying to get under your skin. Until you get those stats, a few ideas for you to respond with; basically, I would challenge them to show a correlation between the raw number of roughing the passer penalties and favoritism from referees (and their implying that equates to favoritism from the NFL.)
First, let's remove Brady from the conversation for a moment. Joe Montana was a great NFL quarterback. He took very few sacks; does that mean the refs were favoring him by not calling holding on his offensive line? No, of course not; what it means is that his offensive line was adept at pass blocking, Montana made good reads, he slid in the pocket well to avoid the pass rush, and he had a quick release. You can't jump to the conclusion that refs favored Montana; similarly you can't jump to the conclusion that refs favor Brady.
Second, let's talk about pocket presence and how that relates to getting hit. The best NFL quarterbacks have much better awareness in the pocket; that in turn results in them getting rid of the ball in a more timely manner than quarterbacks that don't have that sense, that end up taking huge hits. Those big hits are more likely going to draw a flag, so QBs like Jason Campbell and Chad Henne and Joey Harrington are probably going to draw more RTP flags, and have a higher percentage of RTP penalties.
If you look at year by year fumble leaders you see a correlation between guys who either have poor pocket presence or make poor decisions with the ball most often leading the league in fumbles; those same guys are going to get hit more often, and draw more RTP flags.
There is this study from a couple years ago that was done right after opposing fans were convinced Brady was the beneficiary of favoritism after that Ravens game. The conclusion was that marquee quarterbacks do not receive favoritism; Brady was among the top five in receiving RTP flags only once in five years.
Smarter Stats: The Brady Rule Effect - The League at washingtonpost.com
Also, if you are debating the topic with a Ravens fan, the follow up column shows the Ravens were not among the most penalized for RTP penalties over the five years of that study:
Smarter Stats: QB Protection Nothing New - The League at washingtonpost.com
Now if somebody says something about percentage of RTP flags per sack, I would respond that there is no correlation between the two that would lead to concluding favoritism. Again, the better quarterbacks avoid sacks and big hits; the ones that are not as smart take too many sacks, lots of big hits - and more big hits equals more RTP flags.
One last thing regarding the offensive line and protection: through the Bears game Brady has been sacked 21 times and has taken 41 hits this year. With that small a number of times of being hit, I seriously doubt the Pats have benefited from very many roughing the passer penalties this year.
Brady Avoiding The Big Hits - Mike Reiss - espnBoston
Of course if you mention that, your friends will simply move the goal posts and say that is "proof" the refs favor Brady by permitting the Pats o-line to hold.