To say Trump is wrong is becoming something of a mantra, but let's look closer at why he's wrong.
Yes, weakness might embolden terrorists, but strength threatens them, causing them to react.
I would never make the masochistic argument that the United States creates terrorists out of the otherwise peaceful thin air. However, violent people react to violence. If representative government insists on committing violence on behalf of other people, then those other people will always be targets of violence, because they're less protected than those who represent them. They're more protected because they count as more than one person (among other reasons).
Terrorism is certainly a channel of violence, but it's only one of many. If someone wants to go to another place and kill murderers, so be it, but don't represent me. Let the Trump empire or the Clinton empire or the Obamas and Bushes of this world act on their own behalfs.
Trump promises the same tired solution Obama did and which Clinton already does. They want to end war, which for some odd reason specifically involves going to war. I have no faith that Trump will get less children and civilians killed as either of the Clinton's, Obama or Bush have.
A strong Hillary is as much of a problem as a strong Trump. Terrorism thrives not on weakness, but the abstractions of impersonal, representative strength.