It’s not Israel per se, it’s that these protests could metastasize into general anti-establishment ones. Israel is just the flashpoint.
In case you’re wondering why the authorities didn’t really care about the Convoy is because, frankly, most of the authorities agreed with them. Right-wing protests are inherently pro-establishment, and often have the tacit, if not explicit, support of the police, whereas left-wing protests certainly don’t. The tell, with the Convoy, is that no one was going to do anything until the Ambassador Bridge got blockaded: then it became about money. Otherwise, everyone was perfectly content to see rich, white suburbanites having a tantrum. Fascism, after all, can be good for business.