It could be said that in Sylas' entire life, Pride had been the one root cause of all his actions. Whether it was times he chose to be his best, or times he couldn't be bothered to do that, they were all dictated by Pride.
He felt that it was only natural he felt this way. Was he not better than most he came across in most things? Was it truly a Sin to feel Pride for such things?
The problem with Pride was when it was steeped in arrogance—an overblown sense of worth that tried to uplift skies that were well beyond your height to reach. What was wrong with Pride in itself?
It could be said that this was the same for all the other Sins, no? Wasn't the problem that they were taken too far sometimes and not that they existed?
Everyone needed Greed. If you wanted for nothing, what purpose would you live in life? Even if you just hoped to live out your days in peace, wasn't that still a form of Greed? It was just an accepted form.