One can certainly file preemptive law suits to seek declaratory judgement that any granted patents are invalid and/or unenforceable. This had been done by some companies who felt there was risk to their business from certain patent owners.
A troll typically holds 100s of patents and always on look out for opportunity to cash them out. If they are preemtively slammed with 100s of lawsuits for each patent they hold, their legal resources would be overwhelmed without possibility of huge rewards. It would be hard to imagine that they would be able to keep shop open for long time when everybody is attacking them for no apparent reason.
A troll typically holds 100s of patents and always on look out for opportunity to cash them out. If they are preemtively slammed with 100s of lawsuits for each patent they hold, their legal resources would be overwhelmed without possibility of huge rewards. It would be hard to imagine that they would be able to keep shop open for long time when everybody is attacking them for no apparent reason.