Opinions differ on this. Basically comes down to personal choice.
But, if you know that your cat is in danger by living outdoors, due to predators or neighborhood kids that torture animals, then, yeah, I'd say that's irresponsible.
But, that's just me. Lots of people have no problem with having their cat possibly eaten by coyotes, or whatever.
So, back to personal choice.
Well, I see that I've been NO help whatsoever..
all of my cats were allowed in the house and outside when i was growing up.
all of them ended up dying by either getting hit by a car or being poisoned.
when i moved out, i kept my cat in at night, but let him out during the day.
my vet always gave me grief about it, but, i had a small place, and didn't think it was fair. luckily, he was quite scrappy, nobody messed with him. even the rottweiler across the street was terrified of him!
but, when i moved to the mainland, I decided to keep him inside. Back in Hawaii, I only had to worry about mongoose, rats and other cats, (and mean kids, he got shot by a rubber bullet!) but here, there are a lot more predators, plus rabies. I just couldn't bear the thought of losing him to one of those, so he became a house cat for the last 4 years of his 15 year life.
again, i've probably been no help! sorry.