The disciples knew that the Pharisees, by their influence, could prove formidable enemies, so would have thought it prudent to conciliate them. The Pharisees had taken offense, because the doctrine of Christ was subversive of their traditional customs, regarding frequent washings.
Jesus' disciples realized that the Pharisees, through their social standing, could be formidable opponents, so they would have thought it wise to smooth things over with them. The Pharisees took umbrage because Jesus' message challenged their long-held traditions regarding ritual cleanliness.