China didn't fire the first bullet in this war. China never want trade war, whether it is with the US or Europe. But if they attack China with tariff, China need to come out with counterattack, otherwise China could end up as punching bag.

As for stimulus, China just launched one, and it will take time for it to ripple through economy. Launching another one won't turn the table anytime soon. Confidence and stock market will improve once people start to spend. The stimulus should aim to encourage people to spend domestically, not to encourage businesses to export more, so I don't think trade war has anything to do with launching stimulus. In fact, if people start to spend and Chinese market improve, it could help China case in trade war, there is a powerful leverage since the sick EU will want to capitalize on Chinese market improvement.

Anyway, tariff is indeed the worst possible tool, and at least the Chinese and Europeans are negotiating.