Yes, corn can be taken by diabetic patients.
It's A good source of energy, vitamins, minerals and fibre and low on sodium and fat.
Having diabetes means, the focus should be on the glycemic index, 52 is the GI of corn which is much lesser than corn tortilla, popcorn and cornflakes.
However good may a food, it is necessary to stay at a limit. Same goes for corn, corn taken in limited quantity does no harm.
According to studies, a moderate intake of cron about 10 gms in a day reduces glucose and insulin response and improves digestive health and reduces the risk of chronic diseases.