I did tell him I really like the product and the work, but the whole time he just went back to "You didn't update your LinkedIn profile. That tells me you are not 100% committed." and I couldn't get an answer out of him about the expectation to constantly work overtime; this was never mentioned in the interviews, offer, or during the last 6 weeks.
Another thing I just remembered about our conversation -- I've been doing freelance work for 6 years, and have continued to do so despite full-time employment in the past 3 years. I make sure to keep them separate though, I do not work on freelance stuff (including answering emails/phone calls) during the time I am at work, and I make sure I don't leave early just because I need to do freelance work.
He seems to attribute that also towards me not "giving 100%".
I'm quite frustrated right now, and since I've never worked in a startup like this, not sure if what he's saying is really justified at all. I have made sure to speak to him civilly though, especially when he kept saying I wasn't "100%" because of the LinkedIn and lack of excessive overtime (I was pretty ticked off but I still asked him why and explained my point of view).