There is a fair bit of nuance here, so I'm going to try and clarify a bit of what's going on for those that haven't been following. I'll attempt to provide sources as much as I can, and for some context, I live in Ottawa.
The protesters arrived on January 29th, with a rally at Parliament Hill. The original protest was largely peaceful, in the sense that the majority of the protestors did not harm or assault local residents. However, there is photographic evidence of a protester carrying a flag with a swastika on it[0] and at least one protester with a Confederate flag (who was later asked to leave)[1]. Other objectionable reports include drinking and dancing on the Tomb of the Unknown Soldier, and protesters assaulting and harassing members of soup kitchen[2]. These initial actions didn't exactly endear them to the locals, but in truth, this was surprisingly peaceful given how bad things could have been.
Beyond the first day, however, things largely got worse for residents of Ottawa. Describing things as "honking" is understating it; for the first two weeks, anyone within a few blocks of the protest had to deal with loud truck horns, and aftermarket "train horns", blaring throughout the majority of the day and night. There is documented evidence[3] that long-term exposure to noise is detrimental to human mental health, so for folks living in this area, things have been horrid. Additionally, idling trucks for so long harms the local air quality, especially in buildings that aren't particularly well-sealed... which tend to be occupied by less well-off folks that are either renting or can't afford to retrofit their home.
I won't go into every single case, but in the subsequent few weeks, there have been cases of attempted arson[4], cases where protesters are attempting to handcuff the doors closed on another building[5], and various reports of folks being harassed for wearing masks, for having the pride flag displayed, and more.
The Ottawa Police Service has been completely ineffectual here, doing nothing more than asking protesters or warning them to leave, but not actually taking any enforcement actions against protesters. Even when a court-ordered injunction against honking horns was granted, the OPS has not enforced it.
Additionally, Doug Ford and the Ontario government have been completely absent, skipping 3 straight conferences on how to deal with the protests[6] in Ottawa.
I'm personally deeply uncomfortable invoking the Emergencies Act here. But it's also true that this is probably one of the last remaining mechanisms to actually deal with the protests - not to prevent protesting from happening, but to ensure that they're not harming the lives of local residents that have their own right to safe, secure, and peaceful life. If the OPS or Ontario government had acted in any meaningful way, this would likely have not been necessary.
[0]: https://twitter.com/YoniFreedhoff/status/1487517973422223374
[1]: https://www.washingtonexaminer.com/news/man-with-confederate...
[2]: https://www.independent.co.uk/news/world/americas/convoy-tru...
[3]: https://www.factmag.com/2016/10/09/sound-fear-room40-boss-la...
[4]: https://globalnews.ca/news/8600592/trucker-convoy-police-inv...
[5]: https://twitter.com/AndreaHorwath/status/1492945668838723593
[6]: https://www.cbc.ca/news/politics/ford-trilateral-ottawa-bord...
(edited for spelling/grammar)