Can you persuade me from Agnostic to Atheist?

[Ben Davis]

Don't conflate those; they are three different things. 

Not necessarily

Antitheists are against theism.  They think it would be better if theists deconverted.

Not necessarily. The base definition relates to any position in opposition to theistic claims. Consequently a gnostic/strong atheist is an antitheist. There are further actions that could result from antitheism, such as the idea you listed, but those are not required to be an antitheist, just that you believe that god/s do not exist. This is an example where terms pick up additional baggage, as 'atheism' has.

Gnostics know (or think they know) whether gods exist.  You can't be a gnostic weak atheist, because that would mean you knew something without believing it.  So any gnostic atheist is a strong atheist, specifically one who believes gods do not exist, and who also knows (or thinks she knows) that gods do not exist.

I already understand the definitions. I spend much time correcting people on them

Strong atheism is just believing that gods do not exist.

As is antitheism.