I worked for a small company (we were always in ‘start-up mode’) that stocked beer in the fridge and celebrated beer Friday. I can’t stand beer so I would politely pass on the beer and drink my diet soda. I watched in horror one day when they served not one, not two, but three beers to an underage employee. The owners of the company considered themselves beer connoisseurs so they justified sharing their libations with this 19 year old. I was shocked. Holiday and office parties were always stocked with booze. I am not a teetotaler and enjoy a glass of wine with a meal but office drinking can end up excluding people as often as including them.
One thing I would point out is that recovering alcoholics are generally covered under the Americans with Disabilities Act (ADA). Disclosing a disability to a supervisor or to HR triggers a requirement for confidentiality. Any company with 15 or more employees is subject to the ADA, start-up or not. Many state disability laws cover businesses with only one or more employees. Your manager probably violated the ADA when he derided you publicly for not drinking.
The problem with start-ups is that you are often working for children who have no real business/life experience. Just because someone is leading a new venture does not negate the necessity for courtesy and common decency.