Sinning in the will of God

Acts 1:20 [speaking of Judas and how he betrayed the Lord]
“For it is written in the book of Psalms,  ‘Let his homestead be made desolate, and let no one dwell in it’; and, ‘let another man take his office.’

QUESTION:
“If Adam’s sin was all part of God’s plan then his disobedience was actually fulfilling God’s will and therefore, not really sin.”  Can it be sinful to do the will of God?  In the same way here, it was prophesied that Judas would deny the Lord.  This was part of God’s plan of salvation for mankind and yet Judas is condemned for carrying out God’s plan.  Doesn’t that seem unjust?  The answer isn’t really that difficult to understand. Continue reading