Abu Bakar Bashir has shown himself time and time again to be a despicable human being with his message of hatred. Not being an Islamic scholar or having read the Koran I can't say exactly what it says about how Allah deals with sin in the here and now. There is certainly precedence in the Old Testament that events in history speak of God's judgment. The biblical accounts always claim that the statement comes first, the event afterwards.
In what sense then can the recent Java landslides and floods be due to "immoral acts"? Floods are a regular part of monsoonal rainfall. Since many meteorological phenomena are self-organizing or scale invariant, which is exactly to say that there is no preferred scale. A lot of rain is no more or less significant from a physical point of view than a little rain, it just doesn't occur as frequently.
This means that floods are part of life; how can one tell when a particular flood is specifically an act of judgment - as opposed to any general idea of punishment. Perhaps this is the best of all possible worlds with regards weather? Landslides are also a natural result of flooding, but exacerbated by deforestation. You might call deforestation immoral or simply stupid - but people like Bashir probably don't have a doctrine of creation that allows one to speak of the issue at all.
No doubt he means behaviour that doesn't follow his narrow interpretation of Islam. Beware a simple mechanistic understanding of the way the universe operates in a moral sense. I don't know if the book of Job is read by Muslims, but Bashir could certainly learn from it. Whatever your belief, perhaps some well wishing to those currently suffering from these events is far more spiritual and religious than this kind of finger pointing.