What do you do when your team leader does not know why the following is wrong:

a.SomeProp = a.SomeProp; // no funny side-effects, plain old property

He claims 15 years of programming experience, and 7 years of C#/.NET.

To me, someone of 3-6 months experience should know this.

What I have done:

1. Tried to make him understand why it is wrong. He told me not to criticize him.
2. Told him it's not about criticism, but project risk. He got upset with me.
3. I have addressed the risk of this person with our manager (few weeks back).
4. I have addressed my concerns with this person with our manager several times, since 1 month after I started there (7 months now).

Currently, I just feel like just not going back to work... I hardly have any nails left, and this is really just the tip of the iceberg.

As nothing has changed after I have spoken to the manager for the last 6 months, I feel like I need to make some sort of ultimatum.

Do you have any suggestions?

PS: Please do not make this subjective. I have no need for arguing. The level of incompetence is pretty clear. I just need some advice before going insane.

Update:

Thanks for all the answers (trying to update before close, buggers). I think I will forward this thread to our manager :)

Update 2:

I sent my manager another mail with my concerns, and a link to this question. Awaiting response.