# It is necessary to stop them

"They must be prevented from spreading their teachings" or "They must be stopped from influencing others by their words"

# are upsetting whole families

"are ruining whole families"

# for disgraceful profit

This refers to profit that people make by doing things that are not honorable.

# what they should not teach

These are things that are not proper to teach regarding Christ and the Law because they are not true.