Many people here do not believe that there is such a thing as evil in terms of actions. Carnal perhaps. It would be a very animalistic thing to do. We are above that in respect that we do not need to give into such urges.
Lust is the first step to falling in love. No matter what anyone may say, the first thought they had when they saw the man/woman of their dreams was most likely sexual. I believe the best "lust/love" spells are those that enhance what is already there and not create what never was and never naturally would be. This way, when the dust settles, the reasons for the actions taken place are still validated in their mind. They may have normally never acted on their feelings, but since they were provoked to, if they are pleased about the results, they will continue on their own and you can feel good about what you have with the person.
Mind you, I don't work lust/love magick, but this is how I would approach it if I did.