Decency -- I have heard people use this word all the time to depict what people really are like, maybe in their own terms, or just plain blanketing. The same goes with indecency. In your own terms, definitions, experience - or whatever you choose to use as a yardstick - what does a 'decent' guy/girl mean? What does an 'indecent' guy/girl mean? Give your explanations if you have any.
Going by your expression, can a supposed 'decent' guy have a relationship with an 'indecent' girl? Also, can an 'indecent' girl have a relationship with a 'decent' guy? Should dating exist between only 'decent' girls and guys, and also, between 'indecent' guys and girls, going by your explanation of course.