I prefer not to dispute comments of this nature, particularly when they were posted a while back, but this statement, as it stands, really needs some qualification to prevent misleading those just beginning their research. The "facts" shown are easily disproven, the statement way too broad, and the context unclear.
For hundreds of years the Fullerton name has been found throughout Scotland and northern Ireland (even in England, in fact,) and found in particular concentrations in Ayr, Arran, and Bute on the west coast and Angus, Kincardine, and Aberdeen on the east coast. The gentry families are often easy to trace because of their inclusion in various books (e.g., Burke's Peerage) and others with no obvious relationship to the gentry can be found by the dozens before 1700. Coincidentally, I've found relatively few in Argyll although I'm sure they were there.
And as far as "most of" the immigration coming through Ontario - total nonsense. Fullertons can be found in heavy concentrations in eastern Pennsylvania and eastern Canada (e.g., Nova Scotia) in the mid-to-late 1700s. My own came through eastern Canada in the late 1700s and have spread throughout North America; others have been just as prolific. And yes, coincidentally I also have found some in my line who immigrated much later from northeast Scotland to Quebec and Ontario in the time frame you mention.