Leftist philosophers

Why do left-wing philosophers feel it acceptable to jettison their philosophical skills as soon as they start talking about politics? Philosophers who are normally very good start making "not-even-minimally-respectable" arguments. They stop considering every possibility, they make assumptions which are clearly false, and they make invalid moves.

Here are two examples:

Stephen Law posts these two articles about traders losing money relative to the market.

Some commenters point him to the Efficient Market Hypothesis.

Law is ignorant of the fact that even in markets where the market is going up (i.e. the average investor makes money), the median investor loses money.

It's hard to beat the market. But what causes the market signal in the first place? That's right. Savvy investors who find information not already incorporated in the market price, and incorporate it into the market price.

Raymond Geuss posts this "brief guide to recent health-care plans" in the UK.

He describes that healthcare in the US as a "free market". It isn't remotely. Therefore, his argument that "Efficiency in this area is one thing ‘free markets’ cannot attain" is not even minimally respectable.

The rest of his argument is similarly bad. For some reason, he thinks that putting healthcare management "out to tender for the most efficient bid" will lead to "costs rising".

For some reason he implies that profits are bad. He ignores whether it is possible to make a profit and improve quality of healthcare (it is).