Sajda to mankind (Adam) is sajda to God (Allah). Those who don't do sajda to mankind (Adam) are iblees, satans, kafireen (الْكَافِرِينَ) and are arrogant (اسْتَكْبَر) - this is the short message of parable of Allah, Adam and Iblees. Such people divide humanity and make sects in it.
Shajar الشَّجَرَةَ are branches that divide humanity. Adam was prohibited to come near it.
Ego / Pride (iblees & shaitaan) don't let us do sajda (love, respect, accept, accommodate) to all human beings (Adam) that's why iblees is called shaitaan (one who cannot see the hidden truth / blind in arrogance) -
Service to Mankind is service to God, this is the basic message of all religions but we forgot -