An unfriendly person pursues selfish ends and against all sound judgment starts quarrels.
OJBA man who separates himself seeks his own ta'avah (desire); he defies all tushiyyah (wisdom, sound judgment).
T4TThose who separate themselves from other people think only about those things that they are interested in; if they would continually associate with those who have good judgment/sense, they would constantly disagree/quarrel with them.