It can be morally wrong, but only if the lustful thoughts are about someone of the opposite sex.

Only actions can be judged, not thoughts. Evil is when someone decides to harm others, so in themselves thoughts can’t be evil. They can lead to it though

Thoughts, desires and emotions are neither moral nor immoral because none of them causes well being or harm to others.

Actions and their consequences are what can be moral or immoral.

Atheism is unbelief in gods. It's not a system of morals, nor is it a lack of morals.

Not at all   .

So thoughts are a crime in your religion. Having thoughts isn't bad or a crime, the actions that might lead to actions. The actions are the issue, not thoughts. You can't be prosecuted on thoughts, nor should be judged on them, it is totally ridiculous. Having thoughts lustful or not is being human

In their own view: Atheists believe in Abortion and Divorce and Theft of Non-Tangible Property (as well as total Bodily Autonomy from the surrounding Environment) so it's okay to Lust except where the Consequences of getting caught would be worse than the expected reward within a specified time frame. 

In God's view: they have a Conscience and know right from wrong but often choose not to do what's right. Sometimes they choose to do what is righteous because The Spirit and Law of God in their Hearts compel them to though.

Without lust few babies would happen.

Oh, the only thing every atheist has in common?

We don't believe in gods or pixies.

I know you won't process this.

~

Lust is how we all got here!  I've always believed there's nothing wrong with fantasies as long as they remain just fantasies. 

Back in the 50s, there was a song about 'Standing on the corner, watching all the girls go by', and it had a line in it 'You can't go to jail for what you're thinking.'  I wonder how many Christians would want 'thought police' if that was possible.

(I'm not an atheist, more of an agnostic.)

No, it's unavoidable and it hurts nobody.