By using such terms, you project your biases onto the situation. You impose some sort of model for determining what is or is not aggression, which is not a universal constant, but a preference that you have adopted. You therefore propagandize yourself with your own language.

Let's say, for an example, a person cuts down a tree and fashions the wood into a table, and some other person comes by and picks up this table and walks away. To say of this situation, “A thief has stolen that first person's table” is not an objective, value-free way of looking at this situation. Moreover, to describe either person's actions as 'aggressive' and the other as 'defensive' is not an objective, value-free way of looking at this situation. In either case, what you would be presupposing is the legitimacy of the first person's claim to ownership of that table, and the legitimacy of a standard which says that the act of building a table necessarily grants one the right to ownership thereof.

This is often, in the case of more casual conversation, not problematic, for the values being presupposed are not of any particular interest. In this case, however, the values being imposed by your language are precisely what was in question to begin with.

Consider the two cases: a person destroying the private property of some random business, and a person refusing to pay taxes. What makes the first action 'aggressive,' in your mind, is that the private property in question belongs to the mentioned business – obviously the people perpetrating these acts, being anarchists, think differently. And what if they're right? By your standards, that is. Put differently, what if this business had received government subsidies? What if it benefited from unfair regulations? What if it lobbied the state to help take down some of its competitors? What if it was contributing to funding the country's military efforts, leading to loss of human life around the globe? Let's say we measured the overall impact of these things, the total cost that was being imposed onto the UK population, and then accounted for how much of that population these anarchists made up. How long until they're no longer acting aggressively but instead taking back what is 'rightfully' theirs?

And in the second case, you suppose that evading taxation is 'defensive,' which so tells me you deny the state having any legitimate claim on the funds being captured – if this were a universal constant, I'm sure you'd be very pleased, for the expression of your ideology would become wholly unnecessary. But again, you only assume that which you then set out to prove. You say that defensive action such as this is justified – but why is it defensive in the first place? Well, because you consider it justified. Similarly, aggressive action such as that of the mentioned anarchists is unjustified – and what makes it aggressive to begin with? Why, only that you consider it unjustified. It's circular logic, albeit a stealthy instance of it, and one that often gets passed off as actual reasoning among less serious political thinkers.