Which British politician agreed with Sam Adams and the other revolutionaries regarding their grievances with the British Parliament's imposition of duties and other acts on the American Colonies?

The politician you're thinking of is Edmund Burke. He was born in Ireland (it's important to remember that at this time Ireland was under British rule; Northern Ireland still is) and moved to London after he gave up on his law studies. He was brought up in a religiously mixed house. He was a practicing Anglican and his sister was a Roman Catholic. In most households at this time, this would have been a strong point of contention. But perhaps it informs the type of pragmatism that Burke brought to the British Parliament when he was elected in 1765. He knew firsthand what British rule looked like. Perhaps that's why he sided with Sam Adams and his compatriots as they petitioned King George III and the Parliament for redress of their grievances. Originally the American Colonies had no desire to be a separate country. They were, after all, loyal British subjects. However, as the Parliament demanded that the Colonists pay for, and perhaps not unreasonably so, the French and Indian War (what the British termed the Seven Years War), things turned sour. American colonists, particularly those who were well off, didn't like the idea of paying additional taxes for their general welfare. Burke saw that the Parliament was being inflexible when it came to the imposition of taxes or duties.American colonists called for a seat in Parliament and Burke thought that more flexibility by Parliament would help maintain a positive relationship with the king's subjects across the Atlantic, but it was not to be. 
http://americainclass.org/sources/makingrevolution/war/text1/burkereconspeech.pdf

http://www.bbc.co.uk/history/historic_figures/burke_edmund.shtml