I think it's hard to accept that the NBA is refereed this way, but it's something you either have to do as a fan or stop watching, because it will drive you insane. Draymond should absolutely not be allowed to act that way, but he knew he would because of the situation: now 1-0 at home, with the first quarter going in the Celtics favor.
What can the Celtics do? The simplest answer is that Dray won't be allowed to get away with this stuff every game. I think of these technical fouls reviews as a little bit like mock executions: the NBA of course wants seven games and wants Draymond out there, but if he keeps behaving like this, he'll have to sit. He's been ejected in the finals before, after all. There's a certain point where the conversation becomes all about refereeing and the NBA knows that's not good for the product. You can get away with a refereeing hack-job like this in two games a series, but not three or four, or people stop watching.
The thing is, Draymond knows this too. In addition to being a psycho, he's very smart. He knew he would be able to get away with murder tonight, and he knows he won't be able to get away with the same nonsense in Boston, so he'll dial it back. And if he's not allowed to hook people on screens or bulldoze Grant Williams, the Warriors will have an enormous problem playing defense and getting Steph open because the Celtics are younger, more athletic, and on the whole the more talented and deep team.