On multiple occasions, the actor and reality TV star has lashed out at the "haters," "cowards" and "sick people" behind the cruel comments he and Spelling have read on social media.
But in the latest episode of his "Daddy Issues" podcast, McDermott revealed they aren't the only members of the family who've read those critical comments. Their 12-year-old son has seen them for himself — unfortunately.
"I hate social media — I hate it, I hate it, I hate it!" McDermott said, adding that "it's a necessary evil" for people who work in the public eye.
But there's no need for it to be any kind of evil toward children. Still, McDermott remembers one time when commenters were particularly unkind to his kids after Spelling shared a photo of them on Instagram.
"The kids got bullied for their clothes they were wearing on the first day of school," he explained. "Tori posted some picture of the kids' first day of school, and they're like, 'Oh my god, look at their hair,' 'Oh my god, are those clothes from Target?' And I'm like, what the f---? It's so L.A."
But some of the criticisms went beyond clothes and styling and straight to body-shaming.
"Liam has seen it, and he's 12," he said. "He saw some of that stuff."
And while the proud father stressed that Liam "handled it really, really well," the words still hurt.
"He said, 'Dad, am I obese?'" McDermott recalled. "I said, 'Look, buddy. There are some sick people in the world, and they need to do stuff like this. They need to say bad things about people. Think about it, son. You have a busy life. You have school, you got sports, do you think you have time to go into Instagram, scroll through the people that you're following, and make a negative comment about somebody? No, you don't. You don't, and if you did, you'd fill your time with something else. So think about how sick these people are that they have to do that.'"
The 52-year-old said he "went ballistic" after seeing the comments about his kids, and he fears that Liam won't be the only one noticing them in the future. After all, it's only a matter of time before Stella, 11, Hattie, 7, Finn, 6 and Beau, 2, gain awareness of such things.
But he hopes things might change before then, because "when it comes to kids," they are — or should be — "off-limits."
Until then, McDermott also recognizes and appreciates that not all the comments about his kids are so mean-spirited. In fact, many fans have rallied for them, which he noted during a past social media rant.
"Thank you to all the people who came to our defense," he wrote earlier this year. "You're all kind compassionate souls. Down with the haters!! Up with love!!"