There are quite a few T1s on the US forums that talk about giving blood and seem to have no problems. Perhaps it needs a few 'stroppy' individuals!
most (the rest of the world won't accept our blood though if we were in the UK during the BSE time)
I'm type2 controlled by diet, I gave blood a few weeks ago. They had a word with the doctor and she came to speak to me. She only asked did I have good control, didn't ask when I had tested or what the result was. I'd taken my meter in case I had to check.