This is a message to the UAE. Israel is telling the UAE : you need to pick sides. Hamas is considered a terrorist organization by the EU, USA, and Israel. Had this guy gone to Europe for a transit visit, he would have been arrested. Dubai does not arrest him, and let him and other Hamas and Iranian people pass through freely. So I think this was a message to the UAE before it being a message to Hamas. For long the UAE has been the eye of the hurricane, the calm area in the midst of the storm. It was the middle east Switzerland that tried not to take sides, where enemies could trade with each other. It wanted to remain neutral. However, being neutral may now be viewed as a strategic threat to Israel or even the USA. This may be a dangerous strategy though as it could backfire, and I think the UAE police chief's strong reaction, was also a threat, to the west that is could backfire and that the UAE may move in the opposite direction if Israel/US is trying to push it away from Iran.
Saudi-backed forces advance on rebel-held province in Yemen (DPA)
from the article: Report: German passport tied to Dubai hit wasn`t forged