And who defines swearing? You? Me? Marilyn Manson? I think a lot of people would be surprised to learn that "douchebag" is particularly more rude than "stupid," which you apparently have no problem using. At least that's my impression from the way people tend to use it (and it seems to be pretty near ubiquitous with people my age and younger in the area where I live).
pavel_lishin brought up a great example above: sucks. To most people under the age of 30, it is categorically not swearing. It is not even slightly naughty. It's informal in much the same way that "totally sweet" is, but it's not dirty. But many people older than that will insist that it's swearing. True story: Once, when I was working on my college paper a few years ago, we used "sucks" in a headline. The faculty adviser flagged the headline and questioned whether we wanted to use swearing there. Every single student there was baffled by what she meant.
I think you missed my point somewhere. I swear quite a lot. But a lot of people are easily offended by words that wouldn't bother me. A standard some prostitutes use is to wait until their client tips their hand as to what sexually explicit words to use. Some men think "dick" is perfectly acceptable but "cock" is foul language. For other men, the reverse is true. So, yes, I think if your goal is to grow an audience, you are behaving stupidly if you do not stop and think about what kind of language will likely get negative reactions.
I am aware that words like "retard" or "stupid" can be just as problematic as words like douchebag, cock, or dick. But in this instance, I think it conveys what I mean better than any other word I could use. I am not against the use of strong or loaded words on principle. I just think unnecessary use of such language is a good way to shoot yourself in the foot. I can't imagine someone wanting to lose audience members or even risk losing them without good reason.
I am guessing you didn't read my blog post on the topic. That might explain why I am baffled by your reaction.
pavel_lishin brought up a great example above: sucks. To most people under the age of 30, it is categorically not swearing. It is not even slightly naughty. It's informal in much the same way that "totally sweet" is, but it's not dirty. But many people older than that will insist that it's swearing. True story: Once, when I was working on my college paper a few years ago, we used "sucks" in a headline. The faculty adviser flagged the headline and questioned whether we wanted to use swearing there. Every single student there was baffled by what she meant.