Did their king crush Ami?
Rashi: We read "Malkam" like 'Mah Lachem.' Radak - the Hei is 'swallowed' in the Dagesh in the Lamed. Similarly, "Mazeh v'Yadecha" (Shemos 4:2) is written as one word, but pronounced as two. He addresses the officers; they crushed "Ami", i.e. the poor - "Im Kesef Talveh Es Ami Es he'Ani Imach" (Shemos 22:24). They are called "Ami", for they have no help other than Hashem. Not only do you rob them - you even crush their bodies and hit their faces!
What is the meaning of "Titchanu"?
Rashi: You crush and diminish, to despise their cases.
Why does it say "Ne'um Hashem Elokim Tzevakos"?
Radak: He knows your evil deeds. You think that He does not see. He testifies against you about Gezel he'Ani in your houses, and crushing and hitting Aniyim! He sees all, and will judge you for everything, for He is the Master of legions above and below.
Malbim: Hashem asks this (why you are not satiated with money, and steal).
