Choosing not to use the term doesn't mean it reminds people of slavery, it simply means that they choose not to perpetuate a term with negative connotations when an alternative term without them suffices.
You can find negative connotations for a lot of common-use terms.
Have you ever taught African-American kids about database replication? I'm guessing "no", because the master/slave terminology actively interferes with the learning environment — more so than adopting this less common terminology would.
Specifically, American people.
To elaborate, slavery has existed in many times and places and still exists in some places today. Many people have to live with the fear of slavery even now.
No, he means "it's offensive specifically for American people"