Of COURSE Freaknik is offensive- nearly every show on AS is offensive in some way, to some people. And that's why it airs late at night, and has TV-14 to TV-MA ratings for most of its shows, because they are for an adult audience.
Every thing you complained about in Freaknik has already been done in every other AS show- Lois cracks a "Don't trust Whitey!" joke in a Family Guy episode. Uncle Ruckus (no relation) makes every racist slur in the book on The Boondocks. Drug-crazed, Born- Again fruit-people bash open Master Shake's head when Frylock tells them that there is crystal meth inside it on ATHF.
Racism is wrong, no doubt, but being able to laugh at a racist joke can be a good thing- it means that you don't believe in racism and prejudice so much, that you instead find it a laughably ridiculous notion.
Don't take it so seriously!
Freaknik is a parody of the rap scene; the big-booty'd girls, the autotune that seems to be in every rap/hiphop/r&b/etc. song these days, the sterotypical ganja-puffing rapper. Sounds like you need to embrace Freaknik's philosophy of "Positivity-ness"- chill out, have fun, stop hatin', and love and respect your fellow man. That doesn't seem at all offensive to me.