Given that I don't really like complaining about things without offering suggestions for a better way, here are three ways to deal with sectarianism in football. I should note that one of these is radical to the point of being utterly irresponsible.
1) The SFA/SPL could ban all football chants. Instead, allow people to bring in instruments (maybe even issue vuvuzelas to the crowd). This immediately limits sectarianism to those with the discipline to learn an instrument - and when there's trouble, it's considerably easier to remove "the guy with the bagpipes" than "whoever started that chant". (You'd continue to allow cheering, of course - just no chants that have a recognisable tune.)
2) The SFA/SPL could embed a couple more officials in the crowd, and if they hear sectarian chants, have them order the match abandoned. Afterwards, the points get divided based on the nature of the chants and the current score - the default is "no points for either team", but you need some process in place to avoid fans from deliberately getting games abandoned when their team is currently losing.
Or, of course, simply deduct points from teams whose fans do engage in the chanting.
3) Remove the police presence from the inside of grounds entirely. Instead, license the grounds to host football matches. The moment there is trouble, including sectarian singing, strip the club of the right to host matches. That this then provides clubs with a massive problem of fulfilling their league obligations is their problem (they would have to find a new ground, at short notice, and that ground would be at risk of also losing its license).
(If this were done, clubs would have to have the absolute right to ban away supporters if they felt that was necessary. The clubs would also have to massively increase the level of stewarding at games.)
And, yes, #3 is the one that is potentially irresponsible. To be honest, I think #1 is probably the best solution.