Really? I'm not sure there were ever many votes in this country in actively opposing and facing down SFIRA. It certainly did no good in the 1970s for Conor Cruise O'Brien who (just like McDowell) lost his seat while while a sitting minister. Likewise John Bruton's brave anti-SFIRA stance arguably cost him the Taoiseach's job in 1997.
why is it so "brave" to face down Sinn Fein? i think most of the irish people know what they are about and are well capable of making their own choices. If Bruton kept up with his stance and stayed in power there would have been no Good Friday agreement and the ensuing peace. Politicians like Ahern and Blair are also both well aware of Sinn Fein's activities but used a level of diplomacy for the good of the peace process.
There was no silent majority supporting McDowell, we have a secret ballot in this country and the PDs were soundly beaten and the the Shinners picked up more seats than them. There is no other better barometer of public opinion than that. If he wanted to show real bravery he would've have tackled crime in places like West Dublin and Limerick (although i am aware of the provo connections).