I think maybe the more pertinent question is 'why do the churches NOT get involved in challenging sectarianism and racism?'

Why do you think churches do not get involved in challenging sectarianism and racism?

I was viewing Tony's web site 'Peace wall' graffiti comments and thinking of writing large across the Peace wall 'Jesus is our Peace, making the two communities one, having destroyed the dividing wall of hostility'.(Eph.2.14) , and was thinking if the church really believed that, it won't continue to maintain our divisions but rather proactively engage in modelling out this Gospel message within our divided communities.

Why do you think so few churches get actively involved in peace and reconciliation?

I think that so few churches get involved in reconciliation work is because it is not viewed as a central Gospel imperative and therefore not given priority. It is even seen by some as a distraction from the 'real' work of redemption and so is sadly neglected.