What's probably rattled Mr Murphy's cage is the way that directors in small companies pay themselves.
In big companies, the directors get paid a salary for the work that they do, and that's subject to tax and (more relevantly) national insurance. Tax is 20% this year, but the NIC is 11% for the employee and 12.8% for the employer. The salary and the employer NIC are expenses for the company in calculating the corporation tax, which for large companies is 28%. Any profit after tax can be ploughed back into the company, but some of it is usually paid out to the shareholders as dividends. Dividends are free of NIC, and if they are received by a basic rate taxpayer there is no further liability. (higher rate taxpayers pay and extra 25% of the actual cash dividend that they receive, which is equivalent to the difference between basic and higher rate tax)
Therefore management = reward for work = salary = PAYE and NIC
Ownership = reward for investments/risk = dividends = no NIC
Directors get paid for work done, shareholders get dividends on their investment. They are usually different people, although directors can and often do own shares in their company.
In small companies, the directors and shareholders are usually the same people, and although they are in theorey separate from the company, the tax burden in practical terms falls on them, even if it is corporation tax levied on the company. (If the company didn't pay it, there would be more left for them)
Bear in mind that when their salary from the company moves above £6,035 the government collects a total of 45.8p in total tax and NI.
Some people see that as rather unfair at that level of income.
What they do, therefore, is work for a low salary (as is their right) reducing the NI burdens. That leaves more money in the company, which then pays tax on its profits, and leaves more after tax profit to be distributed as a dividend - which of course is not subject to NI.
This can be perceived as paying the directors for their work (as managers) in dividends (which are normally paid to business owners). That upsets some people, who don't seem to have a problem with the 45.8% rate of tax at incomes below the national minimum wage.