We haven't given DS (2.3) any 'straight' chocolate yet, though he has had a taste of hot chocolate and a bit of chocolate cake at parties. We were tres strict about all processed food right through til 18/mo 2yr because it takes that long for a gut to mature and we saw no harm in taking it slow. He's very adventurous and will try anything we're having - the strictness was easy because DP and I are boring health conscious so don't eat processed sugar, super-refined carbs etc. Now he's a bit bigger and food is becoming a more important part of his social experience we are quite relaxed so happy for him to have cake and so on, but haven't changed what we buy for home, so it's all quite whole-food lentil weavery type stuff at home.
That said, chocolate is still off the menu because it contains caffeine and another stimulant (I think it's called theo-bromeine or similar) in large enough quantities that if you gave a race horse a mars bar, it'd show up on a doping test. My line about this to anyone offering him chocolate is that he doesn't need any extra stimulation, though I should confess that it is pleasing to turn down a food which is really nutritionally crap in general terms (they are NEVER offering the much touted 'two or three squares of quality chocolate' which are supposed to be good for us, IME).
Obvs this doesn't go down brilliantly with everyone and I particularly get written off as uptight (which irritates slightly as DP has exactly the same view) but I couldn't give a fuck, TBH. The only people who are bothered by it are people who have a problem themselves - they are either so caught up in the 'treat' idea about food that they think DS is somehow 'deprived' (which always makes me think they really should widen their ideas about both 'treats' and 'deprivation') or they are trying to 'buy' DS's affection/ approval (which I find slightly sad and misguided).
We used to experience more tension from others around this than we do now - no one even bothered to ask about whether he was 'allowed' an Easter Egg this year, and no one bought him an egg. We were at friends for Easter lunch and an egg was sitting on the table for people to help themselves to. DS didn't even recognise it as food, so there was no awkward moment. Stick to your guns, OP, and don't let anyone see you get wound up about it- treat your boundaries like they are facts of life and not up for negotiation and people soon look for something else to criticise your parenting for just give up and move on.