It sounds like that is based on very limited personal experience.
I have been smoking cannabis for more than 35 years and it is nothing but an enhancement to me (well... unless used excessively all day or something). To long time users, it's more like having a cup of coffee than an intoxicant. While it is and we have to be a bit discrete, we don't even think of it as an "illegal drug" when we use it either alone or in social settings, but then, this is Canada where we don't believe American propaganda.
Hippies didn't necessarily die young because of drugs (at least not marijuana and not likely LSD either). There are other common factors and lifestyle choices that come into play. I have friends in their 70's who still smoke cannabis several times a day, by the way.
Most all of the harm from cannabis comes from the drug laws, and extrajudicial mechanisms that serve only to ostracize people who defy those laws. For example it is absolutely disingenuous to test urine for cannabis and use the presence of non pharmacologically active metabolites that may persist for weeks or months, to discriminate against people for employment or any other purpose. Hair follicle testing is even more sinister. They are always testing for past use. Even blood tests, while more accurate, immediate and having the possibility to be quantitative, can detect it for up to 4 days.
Funny how the harm is directly related to society. In places where it's legal/ignored and tolerated, there is far less harm than in an authority driven place like America where the public is so brainwashed that they actively participate in the injustice. You've really got to see cannabis use without the stigmata, to understand this. It doesn't affect your family either, when it's tolerated. In fact it can be a "god send" (not my words) when chosen over alcohol abuse. When people aren't punished by society for it, they keep their jobs and/or businesses, they own homes, have families, raise bright kids who go on to higher education just like "normal" people etc.
The answer to the main question in the article "Do Recreational Drugs Help Programmers?" can only be that it depends on the individual, the drugs in question and the circumstances. It is my opinion that someone who doesn't use drugs would almost certainly be affected adversely if they suddenly got intoxicated or over stimulated and tried to code. Drugs don't affect all individuals the same, either. I know some people who just CAN'T use cannabis for example.