It turns out there is little more uplifting than the sight of a dubious Texas medical clinic tangling with a Welsh schoolboy and coming off worse. The spectacle played out when the Burszynski clinic in Houston – which charges people who are dying from cancer hundreds of thousands of dollars for unproven treatments – took on Rhys Morgan, a 17-year-old pupil at Cardiff High School.

Morgan, who is studying maths, chemistry, biology and psychology at AS level, is well known among a rising army of sceptics as the boy who exposed Miracle Mineral Solution after it was pushed on an internet forum for people with Crohn's disease. The product's website claims it has cured cancer, Aids and malaria. The US Food and Drug Administration called it industrial bleach and urged anyone using it to stop immediately.

This summer, Morgan blogged about the Burszynski clinic after reading about a campaign called "Hope for Laura". It aimed to raise money to send the young mother to the clinic for treatment for terminal brain cancer. Morgan did some digging and was alarmed at the lack of scientific evidence to support what the clinic calls antineoplaston therapy.

Nothing happened until the start of November, when a heavy-handed email arrived for Morgan from Marc Stephens, who claimed to represent the Burszynski clinic. Stephens said he was making a legal complaint and that Morgan's post and related tweets were libellous. He demanded in shouty capital letters that Morgan remove the piece. Other bloggers have received similar mails since an Observer article mentioned the clinic earlier this month.

Morgan sent a nice reply. He confirmed he had read the email and pointed out that he was at school and would deal with it as soon as possible. More emails from Stephens followed. They became threatening. One pointed out it was a FINAL WARNING and attached a satellite view of Morgan's house taken from Google Maps. "You don't email a picture of someone's house to them unless you are trying to intimidate them," says Morgan.

Morgan's next reply seems to have silenced the onslaught. He cited US legal cases that showed the aggrieved must prove malicious intent, he noted Stephen's inappropriate warnings of getting the school involved, and asked which US bar Stephens worked for so he could report him. He then posted the entire correspondence on his blog.

The Burszynski clinic has since suggested Stephens is a web marketing contractor and that no one approved sending the picture of Morgan's house to him. The last Morgan heard came from a firm called Dozier internet law, who said last week that it had been hired to investigate his blog and respond to his queries.

• This article was amended on 30 November 2011. The original said Rhys Morgan is a pupil at Kings Monckton school in Cardiff. This has been corrected.