I Think Lucas has always viewed the EU as a threat to his "creative control".
The simple fact is the EU helped fill that void in between the films when everyone was still hungry for more Star wars, but couldn't get any.
Call it a type of jealousy if you will. His fans got strange ideas from the books. Maybe he sees the EU as the start of the great rift between he and his SW fandom, instead of blaming it on the prequels themselves.
I mean, why shouldn't Skywalker or Solo have gotten married? After all, the whole idea of Jedi being separated from attachments should have died with Obi Wan kenobi. So, Luke being trained at a far later age than most probably would have had different ideas about marriage and so on.
I love Lucas's work and admire him greatly, but his rabid hatred of anything that seems to thrill the Star Wars fan-base that enables them to be co-authors in the SW universe seems obsessive and ultimately self-defeating.