Why was it wrong for the british to tax colonists

It wasn't so much "wrong" for the British to tax the colonists; they'd just emerged from the costly French-Indian war with heavy war debts, and increasing taxes to pay those debts seemed a fairly reasonable action for the Crown. The issue arose in the fact that the crown chose to increase those taxes heavily on the colonists. The US colonies had, until then, enjoyed a large amount of autonomy in governance. By the time tax policies like the Stamp Act were coming into effect, many families in the US had already spent their entire lives in their colonies, and as such, the Crown had a very weak, distant influence in their day-to-day lives. This relative autonomy stood in contrast to Spain's viceroyalties, which - from their inception - were under far more direct control by the Spanish crown than the British colonies in North America.

This taste of self-governance must have made the tightened grip of the British crown that much more invasive and imposing, and the colonial response to its policies reflected a people who felt that their very way of life was under attack.