First, I do not like the term "allow". I don't "allow" my wife to do anything, she is her own person and she does as she wishes and vice versa. We do discuss, and come to agreement, on major things, like swinging. We both love each other enough to not participate in anything in which the other has a problem.
I do trust my wife's love for me, and I trust my love for her, so much so that I am comfortable with swinging. I also believe that part of love IS trust. It is not a stretch to imagine someone using the term "love enough" to mean exactly what I just said. Is what I said qualifying or quantifying love? Yes, it is.
When we first fell in love and married, that trust was not as strong as it is now, and it was not so for many years. Our love and trust grew stronger over many years, and over many good times and bad. Our love matured over time, it did not just occur when we said "I do." Maturity, in general or in terms of love, takes time to develop and we all develop at differing pace, if we ever fully mature at all. For many years we did not love each other enough to have that complete trust in each other and ourselves to be swingers. Now we do.
Swinging is not right for everyone for myriad reasons; moral or ethical issues, social pressure, fear of disease, or of being outed, and many more. There are also people that swinging is not right for because of jealousy and fear that one or both could fall out of love with the other or fall in love with someone else. So, if swinging is not right for someone because of jealousy or fear of love loss, their love has not matured enough to allow swinging to be part of their life. It does not however, mean they love each other any less, just that their love has not matured to the point of complete trust.
In short, I do not have a problem with that phrase because it does not automatically mean they being critical of non swingers. It certainly could be the case that the person using the phrase IS using it in a derogatory manner, but it is not a given.
On the other hand, using the phrase, "IF you loved me enough you would......", or similar phrases, says to me that the person that is using it is attempting to manipulate, in which case they certainly do not love their spouse enough.