Is thinking of committing a sin as bad as actually committing it?

No. Actions are what define a person, not thoughts.

Shh…. the thought police are watching.

No. Like Benny states, it’s a person’s decision to act on their thoughts that will put their integrity at risk.

@Benny

What if you shoot at someone and miss, even though you meant to him them? Is it still a sin?

No. People think of doing bad things, probably all the time. Doesn’t mean they’re bad people, or will actually do those bad things.

@upholstry Well, if you shot at someone and missed, it’s no longer a thought. It’s an action.

Nope. Think all the dirty thoughts you want. ;-)

Viewpoint 1
Having the thought is temptation, resisting temptation is righteous not sinful.

Viewpoint 2
If having the thought is a sin, then acting on the thought is a sin, so now you have committed two sins.

Conclusion
No matter which you believe, the thought without the action is less sinful.

@Benny

What if you had a rifle-trigger wired to a nerve ending, and you ‘thought’ to pull the trigger, but the trigger-mechanism failed. Then you meant to shoot the rifle, but no action outside of ‘thought’ actually occurred?