For guidelines on what counts as "rude or offensive," one of the categories of comments we're encouraged to flag, take a look at the Help page that explains the "Be nice." rule of interaction on Stack Exchange. If you see a comment that you think any part of is
or the like, you should flag the comment, either with the standard reason "rude or offensive" or, if you think more detail is needed for a moderator to evaluate your flag, with "other ..." and your explanation.
Moderators have the ability and responsibility to delete flagged comments that they agree are worthy of deletion by these standards. If part of a comment is truly valuable and still needed (e.g. if it suggests an improvement to the post at hand that hasn't been made yet), and part is offensive, a moderator could edit the comment to remove the latter. If that's the course of action you'd recommend, I suggest you use the "other ..." flag reason and say so.
Don't forget that comments are distant second-class citizens compared to question and answer posts. They're generally not meant to be part of the permanent knowledge repository, so their authors and readers shouldn't be surprised if they disappear when they either aren't contributing to the actual content or when they are in any way harmful.
For what it's worth:
I agree with a comment left by msh210 that your first example is offensive, because it is rude and belittling to the author of the approach it's attacking.
Depending on the context, your second example may be rightly called name-calling and/or bigoted.
The third example, in my opinion, may border on rude, depending on the context, since "Did you make this up?" may be taken as pejorative and accusatory, and may unnecessarily cause its object to take offense and concentrate on personal defense rather than on the content. It would probably be more constructive, there, to say something like "Do you have a source for this, or is it your own idea? I would think ..."