Why would a Loyalist think that the American Revolution and the subsequent migration of loyalists to British North America were warranted?
Most Loyalists living in the Thirteen British Colonies prior to the Revolutionary War did not agree with the new taxation that was by order of the king. Their reaction to their disagreement of the taxes was a peaceful one. They wanted the Colonies to have more of a voice in the decision making processes, but they did not want to fight against their King or create a new government. Loyalists did not fight in the Revolutionary War because fighting the King's military was contrary to their beliefs. They were loyal to the King and to England, though they did not always agree with his policies.
Many Loyalists were alienated from their friends and neighbors due to tensions leading up to the Revolutionary War. In some cases, there were even divisions within families. This alienation, loyalty to the king, and disagreements about the Revolutionary War itself led many loyalists to flee the Thirteen Colonies. Some returned to England, while others went north to what is now Canada. They settled in Nova Scotia, Lower Canada, Upper Canada, and other parts in the east.
Loyalists did not think that the American Revolution was warranted as an act of rebellion by the Patriots against the British Crown. Some Loyalists agreed that the British military forces should engage in war against the Patriots, while others simply wanted peace.
Loyalists felt that their ill treatment by friends and neighbors was unwarranted. Some Loyalists left the Colonies by choice, rather than because of ill treatment. Those who left the Colonies because they felt that they had to most likely felt that their relocation was an injustice.