The short seller who took down Valeant went on TV to explain why he has invested in it, but ended up slamming a different stock

Citron Research's Andrew Left went on CNBC's Halftime Report to talk about why he's long Valeant Pharmaceuticals now, but the interview veered off in a different direction.

Left couldn't stop talking about another drug maker, Mallinckrodt Public Limited Company (MNK).

He says it's worse than Valeant - that MNK is the "real offender in the system."

He even showed up with a $1 million check of his own personal cash, and said he would donate it to multiple sclerosis research if MNK would test one of its two flagship drugs. The drug he was referring to is Acthar, and according to Left it makes up 40% of the company's revenue.

Left famously (or infamously depending on your point of view) brought Valeant's accounting inconsistencies and shady billing to Wall Street's attention last October. That, combined with government scrutiny over Valeant's drug pricing practices, combined to bring the company to its knees.

Worse than the worst of the worst

MNK, says Left, is worse than Valeant because its drugs don't even really work (thus the $1 million check). He says that its flagship products were approved by the FDA at a time when the agency made sure that drugs weren't harmful, but didn't check that they did what they said they would do.

"If Valeant had done what MNK is doing I think they [Congress] would've water boarded [Former Valeant CEO Mike] Pearson," he said.

Pearson appeared in Congress to answer for Valeant's price increases at the end of last month.

"There's no reason Valeant should have to reduce prices and MNK not," said Left.

Speaking of Valeant, Left basically said that he's long the stock simply because he doesn't think it's going to go bankrupt in the next 12 months. Bringing on new CEO Joe Papa makes it look like the company's preparing for a turn around.

"You still might say the stock is uninvestable," he said.

"Would I hold this [VRX] for 18 months? I'd need more information."