I think it is dangerous to allow non stack overflow users to edit our posts. Isn't it?
NO. It isn't. Although, I'll agree that many spammers might take advantage of this and try to introduce spam into post but then the edit will not take immediate effect. If an anonymous user (or a user with <2k rep) suggests an edit, It is put in the Suggested edit review queue and requires at least 3 reviewers or a moderator to approve it. If a spam edit from an anonymous user gets approved then it is the fault of the reviewers and they should be punished.
A request to prevent anonymous users from suggesting edits has already been made and declined. The answer on the request also sums up the advantages of allowing anonymous users to suggest edits