Even people who don't particularly care about the moral aspect (a) may find him untrustworthy (if he's lying in his personal life why would you trust what he tells you in your business dealings) (b) may consider it a weakness that can be exploited against your shared business interests (he could be bribed or blackmailed into dealings which don't benefit the company, or embroil the company in legal problems) or (c) lose faith in his judgement, if he's willing to get himself into such a mess.