I don't know what you mean by Bad Posts in my FB  groups. I'm a member in very less no of Groups.. I  always get Good posts. Because these Groups are started y my known friends.

Bad is a very relative term.... And again it depends on the members and purpose of the group... I have seen some obscene posts in some shopping grp ... But since it's not directly posted to me I dnt need to and I can't block the user. 

If u meant posting on ur wall ... Then u need to be selective of whom you are adding to ur friend list

I have so far not got any bad post that has made me uncomfortable through my timeline since all my friends are known to me..But I o get to see some obscene posts like Divya mentioned in a couple o music groups ..the admin takes the necessary steps when that happens !

I use FB very less. But I'm a member of some groups run by my friend like old Hindi Movies group, India Today group etc. but I never received any bad posts. 

I don't care what people chose to do unless I am involved directly. I have one or two such members in my 400 friends which do not subscribe to my views. But that is theier opinion why should I react to their line of thoughts or LIKE what they write/post.

My interests are movies and  Art. Earlier I was member in a group called Hussain Group.. But not now. A similar kind of Group was formed by one of my Friend. In this group we discuss about old Hindi and Telugu Movies. The same friend recently started "India Today " group. I take part, but not  very regular.  Now he intends to start  " My Page 5 Group. My Page 5 was one social website in which both of us were members.That's all.  In this process never I did get Bad posts

Well by far I haven't faced that sort of a problem but if I face then I will surely Block that user from my account because I want my FB account to look good.

I don't accept friendship from people I do not know and so my FB friends are quite limited, only to those I personally know and so the question of such posts never arise, at least it hasn't so far.

Yes, once or twice and I have blocked them. My Fb friend list contains my school friends, other friends and people well known to me, and virtual friends of various writing sites.

If one is careful and prudent  and exercise care in selecting the friends, the question of Bad posts invading your FB groups will never arise.