Your dad was right! I am a former Merchant Marine Office and actually got the chance to sail on a great lakes carrier in 1964, as a Cadet. It was a wonderful experience.
The problem with the lakes is that storms come up fast and unlike ocean storms that produce large rolling swells. Waves come up fast on the lakes and can be more dangerous than ocean waves.
Also, there is not as much maneuvering room on the lakes, except Lake Superior, which many sailors prefer.
Our local Weatherman just did his schtick, and he showed the winds on the night she was sunk. We had 45-50 mph winds here just last night, and he showed how they traveled from southern WI up to Lake Superior, then there was a shift in the weather and it was actually another burst of wind from Canada that supposedly sunk her.
That's 'Gary The Weatherman's' theory, anyway. ;)