London (CNN) Eminent British scientist Richard Dawkins has drawn criticism on social media for what some say is an unfair comparison between Ahmed Mohamed, the Texas teenager whose school project was mistaken for a bomb, and a young ISIS killer. But Dawkins says he was merely drawing a parallel between their ages.

"HORRIFIED anyone thinks I could POSSIBLY liken Ahmed to a killer," Dawkins said in a tweet Wednesday. "My ONLY point of comparison was their AGES: kids not immune to criticism."

Dawkins, a leading voice in the atheist movement, was reacting to news that the Mohamed family was demanding $15 million in damages and an apology from city and school officials in Irving, Texas, over their treatment of the teen.

In September, the 14-year-old, who is Muslim, was detained, questioned and hauled off in handcuffs after bringing a handmade clock to school, which a teacher thought could have been a bomb.

"Don't call him 'clock boy' since he never made a clock. Hoax Boy, having hoaxed his way into the White House, now wants $15M in addition!" Dawkins tweeted Tuesday.

Don't call him "clock boy" since he never made a clock. Hoax Boy, having hoaxed his way into the White House, now wants $15M in addition! — Richard Dawkins (@RichardDawkins) November 24, 2015

The evolutionary biologist has been vocal in his belief that the case -- which made Ahmed a cause célèbre, prompted the hashtag #IStandWithAhmed to trend, and led to a personal invitation to the White House from President Barack Obama -- was a "hoax."

He has repeatedly insisted that Ahmed did not make a clock but rather "took a clock out of its case and put it in a box," and has questioned the teen's motives in doing so.

@Mukhtarishaq2 He didn't make anything. He opened a clock, took out the innards and put them in a box so they looked like a bomb — Richard Dawkins (@RichardDawkins) November 24, 2015

'Picking on a kid'

When Twitter users chided the 74-year-old scientist for "picking on a kid," he responded by tweeting a link to a news story about a child ISIS killer.

"'But he's only a kid.' Yes, a 'kid' old enough to sue for $15M those whom he hoaxed. And how old is this 'kid'?" tweeted Dawkins, linking to a story about a young ISIS killer beheading a victim.

"But he's only a kid." Yes, a "kid" old enough to sue for $15M those whom he hoaxed. And how old is this "kid"? https://t.co/kjzxGDs5Az — Richard Dawkins (@RichardDawkins) November 24, 2015

The tweet provoked an even greater backlash.

"Richard Dawkins, analogizing a kid who modded a clock in a way he found insufficiently inventive to a child executioner," tweeted Angus Johnston.

.@RichardDawkins, analogizing a kid who modded a clock in a way he found insufficiently inventive to a child executioner. — Angus Johnston (@studentactivism) November 24, 2015

"Am I missing your point?" tweeted Lisajane Ellis. "Because there's no comparison between deception and murder. Disappointed."

@RichardDawkins - am I missing your point? because there's no comparison between deception and murder. Disappointed. — Lisajane Ellis (@DancinJuicyLane) November 24, 2015

"I used to look up to you. Your books opened my mind (when) I was a kid. Now you're doing sloppy reactionary thinking; saddens me," tweeted Renee Stephen.

@RichardDawkins I used to look up to you. Your books opened my mind w I was a kid. Now you're doing sloppy reactionary thinking; saddens me. — Renée Stephen (@ReneeStephen) November 24, 2015

Charges of anti-Muslim bias

Many accused Dawkins, an outspoken critic of Islam, of having an anti-Muslim bias for drawing the comparison.

"And it's just a mere coincidence that they're both Muslim? C'mon Richard, surely you can see how this looks?" tweeted Aaron San Filippo.

@RichardDawkins @oldgrower ...And it's just a mere coincidence that they're both Muslim? C'mon Richard, surely you can see how this looks? — Aaron San Filippo (@AeornFlippout) November 24, 2015

@RichardDawkins @yodat_nioj @oldgrower YEAH, one happens to be a Muslim & the other happens to be a radical Muslim. TOTALLY JUST THEIR AGES! — Ooze (@ItsTheOoze) November 24, 2015

"Why do you hate Mu(s)lims Mr. Dawkins?" tweeted @boringfileclerk. "For some who upholds reason above all, I find your tweets disturbing."

@RichardDawkins Why do you hate Mulims Mr. Dawkins? For some who upholds reason above all, I find your tweets disturbing. — boringfileclerk (@boringfileclerk) November 24, 2015

Dawkins responded by tweeting that two individuals' "young AGES are being compared, nothing else," and that his point was that "simply that being a 'kid' doesn't protect you from criticism."

He later mused that perhaps a comparison to the killers of James Bulger, a 2-year-old British boy who was abducted, tortured and murdered by two 10-year-olds in 1993, "would have been a better example."

How COULD you think I was likening a hoaxer to a killer? I just meant "Only a kid" is not a knockdown defence. Remember poor James Bulger? — Richard Dawkins (@RichardDawkins) November 25, 2015

The response to his comparison, he tweeted, reminded him of when he had said, "I don't have to read Mein Kampf to condemn Nazism." "The numpties (fools) thought I was accusing Muslims of being Nazis!" he wrote.

It's exactly like when I said I don't have to read Mein Kampf to condemn Nazism. The numpties thought I was accusing Muslims of being Nazis! — Richard Dawkins (@RichardDawkins) November 24, 2015