How do smart atheists construct their arguments against God / against believing in God / against theistic topics ?
Smart atheist ? Ok I'll bite.
Since god is an idea. It's impossible to convince someone who does not want to be convinced otherwise, that your position no matter how well you present the case will be accepted.
There is no way to prove it's existence or lack of. That in itself is a good argument, that the lack of evidence indicates that the most likely answer is god does not exist. Until there is such evidence it's just an idea. But the true believer will just state that the evidence is all around us and that we are looking in the wrong places, that we don't understand etc.
So one can construct their argument well, one that might sway the truly impartial. But against believing in god ?
Again the arguments can be made but they are not likely to listen anymore than someone who believes in the lochness monster.
Some theists IMO have a stronger position in their belief to use arguments against. Simply because they are not adhereing to such texts as the bible or quran with obvious mistakes (creation stories) that if considered literal are just wrong. Period. So in those cases it takes someone who uses the texts as a guide to even have a chance to discuss it somewhat rationally.
IOW, if they are a creationist you don't have a chance.
But if you go through the religion forum you should be able to find a ton of good arguments in the back and forth.