Anyone that has been involved with football beyond a 'played highschool' can tell you that the NFL in Toronto will kill the CFL, and greatly effect the game of 4 down football in Ontario, and perhaps eventually, the rest of the country. Whether you like it or not, this is ultimately the result. Anyone selling otherwise does not know what they are talking about, or just outright misleading.
Your assertion that anyone who thinks that the NFL in Toronto won't kill the CFL is "misleading" or "doesn't know what they're talking about" is daft.
The CFL does quite well outside of the GTA, and especially out west and in Montreal, and could probably survive without the Argos. More than likely, the franchise could be relocated somewhere else (Moncton? Halifax? Saskatoon? Quebec?). The TV ratings in the GTA would tank, but given the relative popularity of the league nationwide, the loss of the Argos wouldn't kill off any TV contracts.
Also, the Argos could exist with the NFL in town. Look at it this way, the people that would stop going to the Argos and go to the NFL games are those that just like "football". I guess that would account for some of the 18-20,000 people that attend games frequently, but not a lot. I think most people (and especially anyone who's gone in the last 3 years) goes because they like the CFL game and/or the Argos. I can't imagine, that your average Argos ticketholder will wake up and switch from one game and team to another game and team.
Furthermore, who says that support for the CFL is mutually exclusive of support for the NFL?
It strikes me that most of the people saying the CFL and the Argos will die, are the ones that don't get the CFL or the Argos. They are the ones that always try and compare the two leagues, as though American-style hype and marketing is the only way a league can exist. Nor do they seem to understand the support for teams in markets outside of the GTA.