Love is the wanting good for another person even if it costs you personally. Porn teaches you to want pleasure for yourself, even if it costs someone else. That's not love, that's lust.
The chemicals released in your body and especially brain during orgasm build a closer connection and bond within you to the concepts and people you focused on during it. Pornography trains you to be selfish. Whereas having sex and both orgasming at the same time, focuses your mind on making your partner happy and that mutual self-giving becomes what you crave. Because it's based on love, that same mutual self-giving carries over into the rest of your life, and you find more happiness in giving gifts than receiving them, in doing more chores so they don't have to, etc. That's love.
One might argue that the good sense of joy followed by love is evidence that when one loves someone, one is acting selfish [0], even though he/she might think otherwise.
[0]: People are rational and they wouldn't do things that don't result in more benefit to them than their cost.
Ah, but people do occasionally do seemingly-altruistic things, and by long experience, some of those are worth encouraging.
"Love" in English wears too many hats. C.S. Lewis' Four Loves does a good job explaining how the highest and best use of eros (which can be selfish) is to encourage agape (selfless love).
"The promise, made when I am in love and because I am in love, to be true to the beloved as long as I live, commits me to being true even if I cease to be in love."
I made that same exact argument in college to someone who was just trying to help me see how insane I was. Yes, it's slightly self-serving to love and find joy in love. But of all the forms of selfishness in existence, it's the most acceptable and least blamable one.
I'm not sure that not having porn avoids wanting pleasure for yourself. Isn't that what leads to rape, cheating and various other destructive behaviors?
Conversely, consuming porn, even when it substitutes sex with a romantic partner, doesn't preclude having a loving relationship. As you point out, lust and love are different things. Although they are closely linked for most people, that is not the case e.g. for asexuals.
Unless you don't derive your entire life outlook from it. Plus, there is plenty pornography where both orgasm - if anything the porn actresses' seem unrealistically happy.
The chemicals released in your body and especially brain during orgasm build a closer connection and bond within you to the concepts and people you focused on during it. Pornography trains you to be selfish. Whereas having sex and both orgasming at the same time, focuses your mind on making your partner happy and that mutual self-giving becomes what you crave. Because it's based on love, that same mutual self-giving carries over into the rest of your life, and you find more happiness in giving gifts than receiving them, in doing more chores so they don't have to, etc. That's love.