First, four truths which you may need.
1. Looks are important. People who dismiss this fact aren't being realistic. So, he may like your looks but is too shy to say it, or thinks - rightly - that saying it won't make you do what he wants you to do.
2. People are selfish.
3. That particular guy is most definitely very aware of his unprovidential situation. However, that is no reason not to pursue certain natural needs.
4. Sexuality is a central part of human existence.
Do you know him at all? And you don't like him. Why would you flip about his asking you out, if you don't like him, or haven't thought about you and him in a setting beyond a platonic contact? That makes no sense. If you have no interest whatsoever in him, why would you care at all about what he wants to do with you?
Moreover, you debase yourself without cease. Contradictorily, you hold yourself in a sufficiently high esteem to deem him inadequate as a romantic partner of yours. How do you explain this? Is it that 'only someone of his low nature claims to like you' and that 'this subhuman being had the audacity to ask you out on a date'?
What would the person who 'deserves' you have to be like?