I think your wife is making up excuses for why she doesn't like porn. "There's no love involved" seems like a rationalization. Does your every sexual thought have to involve deep feelings of affection and attachment? That just seems like way too much to ask of a regular person.
In fact, since you're poly, you're probably juggling not just love for her but also loving feelings for other people at the same time. That's a lot of pressure. In some ways, masturbation/porn is just a nice break from that--a sexual release that has nothing to do with love. That's kind of the point.