And
on what are you are basing your opinion of what took place during the altercation, if not the only account of the altercation that we have?
Here you go.
And here's a link to various synonyms for "cold-blooded", several of which are very accurate adjectives to use to describe Zimmerman's account of the assault.
And exactly what are you using in order to make your consideration, if not the one and only piece of evidence available?
We have exactly
one source of information to derive what happened during the altercation between Zimmerman and Martin. And that's Zimmerman's statement.
There is no other evidence that gives us any specific details.
And in that statement, Zimmerman does not describe Martin as acting defensively. According to Zimmerman, Martin attacked him without provocation. And not only that, but that attack as Zimmerman describes it was brutal and merciless. It continued even though Zimmerman describes himself as defenseless and screaming for help, and culminated in Martin making two different attempts to willfully murder Zimmerman.
There is
nothing in Zimmerman's version of events that implies or lends credence to the notion that Martin was at all acting defensively. It is simply and clearly an account of one person being savagely beaten and nearly killed by another.
So I'll ask you this again:
If you think Martin was acting defensively, upon what piece of information or evidence are you basing that opinion?