That the "love" in these verses (Matt. 5:44 ; Luke 6:22) is "agape".
Modern Christianity has virtually made a holy word out of agape as if it's the ultimate love one could have for anyone.
What it really meant was a practical, care-taking love that is done of necessity. You fight for your country and lose your life ......... that's agape love. You don't REALLY feel any particular love for anyone or anything as you're being shot ........ you are there because of duty.
So ........ agape means giving of yourself in order to take care of necessary business.
In that respect, it's prudent to "love" your enemies. You do what is necessary in order to mitigate strife and achieve a mutual goal.
In Jesus' time one of the major obstacles to achieving independence from Rome was their factionalism. Jews were divided and fighting each other. They were split amongst various wannabe Messiahs. If they were EVER to succeed in achieving their goal of a kingdom ......... they NEEDED to set aside their differences. Thus, it was wise advice to "love your enemies".