Probability sample vs Non-probability sample survey

On September 28 the Washington post  under the rubric Opinion Catherine Rampell write a rubric name( https://www.washingtonpost.com/news/rampage/wp/2017/09/28/free-speech-and-good-vs-bad-polls/catherine Rampell ) free speech and good vs bad polls. In this article she talk about how her survey methodology was criticized as a "junk science" just because she used what is sometimes called a “non-probability” sample which is another way to do some polling survey. the critic was made in a Guardian article by reporter Lois Beckett because it was conducted online, using what is sometimes called a “non-probability” sample. let explain the difference between the probability survey and the non-probability survey. A probability sample is one in which each person in the population has an equal or at least known chance (probability) of being selected, while in a non-probability sample some people have a greater, but unknown, chance than others of selection. Probability samples are based on the mathematical theory of probability. But for me I totally agree with Catherine today most of the survey are conducted online using the non-probability sample. And non-probability sample offer more flexibility than the probability survey. A non-probability sample may be more practical for some research projects. For example, there are no lists of all the people who have committed a crime or particular offence, although there are lists of convictions for individual offences. The issue then may be whether you are allowed access to such a list for research purposes. Non-probability samples may be more open to the criticism of not representing a population, but are chosen in situations where probability sampling techniques are either impractical or unnecessary. To conclude at this time the non-probability sample is the accurate to do some polling survey.