A Defense of David
Critical thinkers, hear me out. David was a POS in the way told Lauren that he wanted her to be his girlfriend then cheated on her the very next day. He obviously had serious s-xual compatibility issues with Lauren and the right thing to do would have been for him to either discuss it with her or end it because I don't think any of us wants to be in a relationship where we aren't even having an orgasm (or more if your body works like that) when we're being physically intimate with our partners. That's extremely rare for men with women unless there's serious issues with attraction. I think two issues were at play:
When I studied power dynamics you find that people act completely different when they know they're being watched. David likely didn't want to be seen as "the bad guy" by the public since so many groups placed him and Lauren as the model couple so he behaved how he thought he should rather than behaving how he wanted to behave even though he knew he didn't feel physically that way for Lauren. The producers knew exactly what they were doing when they brought a woman on board that was his type and it made for great TV watching the drama unfold as he had to come to the realization that he couldn't deny what he actually wanted anymore.
David had this weird fixation on trying to stay away from women with body enhancements as though that was a bad thing but body enhancements don't tell you anything about the individual besides the fact that they got their body enhanced. Val is a chemist, and chemistry is no easy subject to study. They threw him for a loop by presenting him with an intelligent woman with body enhancements (challenging his bias about them) because it seems like he had presuppositions about how women with body enhancements are for some weird reason. I don't know his past and I can't speculate but the producers did and so Val was an extremely good pick. Lauren's natural body was something he couldn't get past and for some weird reason he tried to no avail. If you like that, you like it and there's no shame in that.
David was more of a coward in my book than nefarious because he didn't want to have a hard conversation with Lauren and would rather keep up the facade. When Val came he was done and I know the producers were licking their lips. No one made him do that, and there's no excuse for it, but trying to deny your true nature will always end poorly for everyone involved.
Lastly, what David said about s-xual compatibility with Gia and Tim rings true to me. I respect Gia's choice to wait until she's sure, but saying you're in love with someone who you haven't been physically intimate with at all feels disingenuous to me. S-x is an extremely important part of a relationship (unless you're asexual) and David's relationship failed partially as a result of sexual incompatibility.