2) The humour in this comes from the fact that sentence could be taken to mean that the Church is offering to help to kill you!! If you look at it as if it says : "Don't allow worry/concern/stress to kill you - let the Church help (to kill you)!
Most people will read it how it was actually meant - which is that the church wants to just help you, generally, in life and can stop worry from killing you BUT it can be read the other way.
Another example of this kind of potential misunderstanding was a national campaign poster for Oxfam a few years ago. In my local town, the Oxfam shop windows were full of posters which said:
GENOCIDE IN RWANDA - YOU CAN HELP!
Now, we all know that what they meant was "You can help to stop the genocide" or "You can help the people of Rwanda at this terrible time". But unfortunately, it can also be read as if it's some kind of recruitment campaign offering people the opportunity to go to Rwanda and join in with the genocide.
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