Many families of Dutch ancestry fought for the british. Just as the majority of the people fighting AGAINST the Crown were of English Ancestry, people fought for what they believe in, not for their ancestral "group".
Taxes were one relatively MINOR issue. It was not that they objected to taxes per se, they did not. What they objected to were taxes, and a host of other laws, imposed without any representation in Parliament. The American colonists comprised almost 15% of the overall population of "Great Britain" (and the colonies WERE considered a part of Great Britain), but they had absolutely no voting representation in Parliament.
Repeatedly, Parliament attempted to impose the costs of the war against France on the colonies (which had virtually nothing to do with the overall war). They wanted the colonists to pay the full costs of keeping massive numbers of troops in North America, when the colonists didn't see any reason for them to even be there.
But, it was the attempts to impose a total lack of freedom of speech and assembly that finally brought the pot to the boiling point.
As to the so called ancestry of Alexander Peers, I have read everything that your cousin has put out and it is 100% speculation. There is absolutely no proof at all. He takes two surnames that are can be pronounced in a similar fashion, and links two different families together.
There was NO uniformity in the Peers surname. Alexanders brothers spelled the name PIERS and PEARS, which indicates that it could very well be a Dutch name as well as an English one (or possibly French).
It seems that it was pronounced by virtually everyone as "Pears", which is not in any manner related to "Pierce".
Instead of playing "my research is superior to everyone else's", how about providing some actual evidence?
It is so easy to make a claim, but sadly, most claims in genealogy are simply not backed up by fact.
Until there is evidence, that I can go check the records on, that parents of Alexander Peers have been clearly identified, I would have to say that he was born in approximately 1745, to parents that are unknown. That tentative parents have been identified, but not proven.
Until the "evidence" is placed out there, so that anyone can go check the records and the research, it simply can not be shown who the parents of either Alexander, or of his wife, were.