What's the difference between riding around town and commuting? If a bike can carry everything you want to carry and adapts well to fenders if you want them then it's a fine bike for your commute. Maybe the mindset is different in DC since so many commuters (in the general sense, not necessarily bike commuters) live so far from where they work. I commute on a road bike because it's what I enjoy riding. If you enjoy riding your Linus, it's a good choice for you.
Given your reason for visiting the LBS, perhaps the guy was picturing a bike messenger type rider darting in and out of traffic. I'm guessing you don't ride like that. If you did, you'd likely find that the Linus isn't nimble enough. But sometimes a car just right hooks you no matter how you ride and a nimble bike wouldn't help.
Also, 33 pounds is toward the heavy end of the range of newer bikes, but it's by no means unreasonable. In the 70's Schwinn called 30 pound bikes lightweights.