I used to live in the country and my cats went outside on a lesh daily but one night a Fisher came up on the porch and scared them somthing fierce.
It took them a while to get over it and still to this day they stay very near to me if I take them outside, even just to the car to go to the vet.
P.S. A Fisher is a predator native to my area, eg. Ontario and the north eastern united states. They are about the Size of a otter but have the look of a... well they look very vicious
because tomcats dont care if theyre in heat or not, and can be very aggressive when trying to get what they want. A friend of mine had to put her spayed cat to sleep because it was attacked very ferociously by a stray tom.
It is really best for your cat to stay indoors. Tomcats will attack without provacation, they can't help it. Especially during mating season, they will fight any cat in their way. They will also kill kittens so they can mate with the female cat. Her grief shoots her straight into heat.
If your cat does not want outside, best listen to your cat. If he is recently neutered or spayed then the cat has lost the wandering bug, which is a good thing.