Why is it ridiculous? Some people are bigger animal lovers than others. To many people their pets are just as much a part of the family as anyone else. Just because you don't feel that way doesn't make them 'ridiculous'.
I know many people who were told they would not love their pets as much as their children, yet when they had children, they still did. It may be a slightly different type of love, but so what? Does someone not love their parents because it's not 'the same' as the love they feel for their child?
For some people their pets are their whole world and I can't see how that can drive anyone else crazy. Having children does not give you the monopoly over love. Did it occur to you that some people have been unable to have children and have found a maternal love for their pet instead?
I know lots of people who have family portraits with their animals, I think it's lovely.
OP I know you said this thread was meant to be lighthearted but unfortunately I just find this sort of attitude from people horribly elitist and condescending.