Final answer:
Senator Charles Sumner was criticizing proslavery settlers in Kansas & Missouri.
Step-by-step explanation:
Senator Charles Sumner was criticizing proslavery settlers in Kansas & Missouri in his speech. He described slavery as an oppressive force, presenting it as a violation of the rights and liberties of the people in Kansas. Sumner's speech aimed to raise awareness of the negative impact of slavery and the attempts to expand it into new territories.