He's terrified of Mages and thinks they should all be killed. Thinking of having sex with you (your character) to him is like think of putting his johnson into a lion's mouth or something. He's afriad your business would burn his business clean off.
I'm just like Jesus. I save... often! ** I can't give you your opinion. I can only give you mine. ** Ignorance is cured with knowledge. Stupid lasts forever.
I almost wished you could. Even if you hadn't chosen the 'stronger' dialogue option, his reaction is still the same. It's a shame, really--I always thought there was some romantic potential there if a female mage couldn't get with Alistair.