Sigh, the bullcrap people contrive out of their butts...
1. Lars didnt wan't to be seen in an embarassing picture via getting attacked by the gem powered house. This ties in heavily with his character's insecurities of wanting to be cool and popular while lacking the attitude to be so.
2. He was reffering to the fact that people make fun of Rolando for being a creepy conspiracy theoriest. Lars was probably getting flack for being around him or again, not being cool or popular... which his strive for being accepted by the cool kids in the show probably comes from simply not being popular or liked as a kid. I mean, come on people, his only friend was Rolando. That says a lot about his social status.
3. Or because he's mad that Sadie was siding with the house on the fact it attacked him and ruined his friendship with Rolando.
Seriously guys, I know this show loves to push boundries but at least those boundries are visible. This is a shot in the dark and a very stupid one at that.