At the funeral speech, how did Marc Antony explain that Caesar was not "ambitious"?

In Act 3.2 of Shakespeare's Julius
Caesar, Antony juxtaposes (places in opposition) an unambitious act performed
by Caesar, with a refrain about Brutus's (or the other conspirators') belief that Caesar
was ambitious and about Brutus (or the other conspirators) being honorable men.  I'll
put it in bullets:

• Caesar did an unambitious
  act


• But Brutus says he was
  ambitious


• And Brutus is an honorable
  man

Here's an example from Antony's speech,
with the quotes in bullets:

• I thrice presented
  him a kingly crown,/Which he did thrice refuse.  Was this
  ambition?


• Yet Brutus says he was
  ambitious,


• And sure he is an honorable man.  (Act
  3.2.105-108)

Antony uses irony to persuade the
crowd that Caesar was not ambitious and was therefore assassinated unjustly, because he
earlier promises Brutus that he will not directly say anything negative about the
conspirators.  He, therefore, says only positive things about the conspirators, but the
juxtaposition of Caesar's unambitious acts with those positive things, creates
irony. 

And it also creates a mob that riots through Rome
looking to kill the conspirators.