violence is not a solution if you only talk about it.

I wonder if 'Violence is not the answer' might not be more familiar as the original saying.

Also "Violence is not the answer if you only talk about it?"

The sentence is tricky. IMO what may be implied here is:

Is there a reason why you don't like #1? Just asking.

Yes, #6 would be the black-humor version, and #12 is the explanation for why.

SP, das gleiche gilt für "Gewalt ist (doch) keine Lösung" - auch das ist ein Aufruf, Gewalt zu vermeiden. Den ironischen Dreh bekommt es erst durch "wenn man nur drüber redet".

'If you just keep talking about it' doesn't really work for me, because 'just' in that sense normally means '... wenn du doch nur darüber redest' -- that is, a genuine plea to talk more.

Even 'If you only talk about it' is subject to that reading, though to my ears less so. To be absolutely unambiguous, you might have to sacrifice a little brevity and say

Violence is not the answer
if all you do is talk about it.

I don't see how "if you only talk about it" can be misunderstood in the OP's context.

I agree that that's unlikely, as I said.

Even if "if you only talk about it" is not very likely to be misunderstood, I find the solution given by hm -- us in #18 flows better:

e.g. Violence does not achieve anything if / as long as it simply remains a/the topic of conversation.

Wie wäre es mit

violence won't solve any problems, as long ...?

My apologies, I see pengiun already suggested the second half of my suggestion in 21, and hm--us in 18.