What's rude?

I can't tell what's rude anymore. I say 'shit' all the time. I was just in someone's office talking to a speaker phone. My coworker was eating cheerios, loudly. The guy at the desk - a slightly older guy, and technically the boss of cheerio boy and me - complained. He said all the crunching made it hard to hear through the phone. But he also said it "grosses him out." By this time, i'd already grabbed a handful of cheerios. I tried to crunch more quietly. I thought about getting a haircut, cleaning up a bit. On a non-cheerio subject, the desk/boss guy used the word "sucks". Is anyone trying to be polite? It seems like people are less mannered and much less formal than ever, yet more easily offended.