So Avraham tells Lot, "we need to separate; if you go right I'll go left, and vice-versa." Lot chose to go to Sdom, which was wicked.
Had Lot chosen otherwise, would Avraham have gone to Sdom?
The Midrash (Bereishis Rabbah 41:6) states that in fact Avraham chose his words carefully. If he really meant that he would go left, he would have said ואשמאלה (without the yud); but ואשמאילה really means "I will force you to go left" - because in fact Avraham didn't want to live in Sodom. In other words, he wasn't actually giving Lot the choice of direction.
(Still, though, Lot is blamed for accepting this; he should have told Avraham that he doesn't want to live in Sodom either, and they would have worked out some other arrangement.)