What is Patrick Henry claiming "they" are doing?

I am going to assume that by "they," you mean Britain.  Henry makes many accusations against the British.  One complaint is that the British are not seriously considering the various protests, petitions, complaints, and requests the colony has brought to them.  He repeatedly uses the metaphor of the chains of slavery to describe the relationship between the colony and its sovereign. Moreover, Henry observes that the British army has massed troops in the colonies and that British warships are hugging the colonies' coasts.  He expects that the British plan to step up their efforts to keep the colonies under their control through force or the constant threat of it. Overall, Henry makes the point that the British have proven themselves over the previous decade to be unwilling to engage in any kind of authentic negotiations--hence his call to arms.