What most of you are referring to is /b/.
/b/ isn't all of 4chan, it's just the most heavily trafficked board of the website.
Yes, /b/ is the scum of the net and truly a terrible place, however, not all of the site is quite as extreme.
There are several sfw boards on 4chan (though whether people choose to follow that guideline is subjective).
Personally, I browse /cgl/ (cosplay and egl) and /an/ (animals and nature).
However, 4chan isn't everyone's cup of tea. You're of the easily offended nature, then browse with caution or don't visit the site at all.
There's always bound to be something floating around that you won't like.