Everything changes once you accept the offer. All the harsh questions asked during interviews and all the tough negotiations become ancient history never to impact relationships again. Right?

Not a chance. You can't be one person before job offer acceptance and pretend to be someone else afterwards. They will remember what you said and did and who you really are and view everything you say and do going forward through that filter.

Two-faced doesn't work. Be careful what face you show at every step of the way.