Institutional buyers are companies that take money to make money for their clients. The clients expect a return on their investment. Clients are not traders, they are depending on the institution to invest their money wisely.
That would not include stinky pinkies. Others will tell you that 'institutions' 'invest' in penny stocks, but these are the most risky stocks, and if you want someone else to do your trading for you, you probably want them to invest in solid companies, not ones whose outlook changes from day to day.
Your father-in-law was right. Penny stocks are identified as any stock below $5 these days. Institutions won't risk their clients' money on such stocks.
It is meaningless to argue with those on this and other pink stocks about it, they don't even know what the term 'institution' means.