When should "not an answer" be used here on Web Apps?

Question

I flagged this answer and it was declined.

not an answer – 1 hour ago declined - flags should not be used to indicate technical inaccuracies, or an altogether wrong answer

The answer is IMO not an answer to the question, it's an opinion. And it asks a question of the OP in a way that I thought was a bit rude.

That's why I flagged it.

Another issue all together is that he is also wrong. Gmail in desktop mode works just fine on an iPad, that was what earned him an -1 from me.

So When should "not an answer" be used here on Web Apps? If it's not for indicating answers that aren't answers?

Answer 1

As the declined reasons states:

flags should not be used to indicate technical inaccuracies, or an altogether wrong answer

If the answer is wrong down-vote it and/or leave a comment letting the poster know that it's wrong. Once the answer has down-votes it then becomes eligible for deletion by high reputation users and can be removed in that way (if it's not improved or removed by the OP first).

Update

Perhaps there was some confusion over the flag reason. If there are a couple of issues with the answer (you mention opinion and rudeness) then it might be better to use the "other" option and add this information in the explanation rather than relying on the predefined reasons. I saw the "not an answer" and thought that it was an answer albeit an incorrect one. If there had been more information in the flag I would have probably come to the same conclusion, so even if I didn't do anything with the answer I would have marked the flag as "helpful".