Who is the client of Android OS, pencil, smartphones?

You don't need to build specifically for Hezbollah, to start worrying about your risk factors

Where do you think the line should be drawn?

Arguably if your client is IDF your devices are more likely to exclusively end up in the hands of military personnel whereas if your client is "Hezbollah" (whatever legal entity acted on their behalf in this case) an attack would be (and has been) far more likely to injure, maim or kill civilians and non-militants, not just because of the higher likelihood of harming bystanders and family members.

Would a supply chain attack like this against Toyota be justified because of the large market share in after-market "technicals" used by terrorist and insurgent groups?

Yeah, and since most civilians in Israel are part or were part of the IDF, then the comment you're replying to is right. And according to the same logic you're using, said Israelis are totally fair game for an enemy state or organization to target and kill. If killing suspected Hezbollah fighters outside of the battlefield in civilian areas is totally fine, because they could fight Israel, then most Israeli civilians are too according to that twisted logic.

I'm sure you'd have said the same if a few thousand explosive devices went off all over Israel, and Hezbollah said that it was just them targeting IDF troops.