TRP complains that feminists complain about sexual objectification. But do they even know what feminists are complaining about?

And today I've argued with someone, who I expect to be a TRPer, who believed that befriending women because he enjoys spending time with them more than with men would be considered objectifying by feminists and after pondering for a while about how one could even think that this could be considered objectifaction I figured I just let the red side explain to me what they think objectification refers to.

So what do feminists mean when they talk about objectification (or to be more specific what do they mean when they talk about sexual objectification)?