I think the important question now is whether it's irresponsible to build channels that (A) terrorists will find useful, (B) will allow them to look more savvy and attractive than they actually are, (C) seed their ideas to a wider audience than they have - see [1] - and (D) count on less motivated people with nonviolent ideas and less time on their hands to offer countervailing ideologies and "win" the space. The space you're creating and enabling.
[1] People with more time on their hands and/or a more absolute/violent agenda are more apt to find ways to game a system, whether it's a swarm or a newsfeed. Their time and motivation are asymmetrical to the normal functioning of a marketplace of ideas in which good/logical ideas are supposed to outperform bad/emotional appeals. The true question is not whether this platform can or will be gamed, or trying to guess and preempt how it will be gamed, but deciding whether it's immoral to exert your intellect to give leverage to griefers by giving them more visible surface area. If the result is something that only marginally helps average people but drastically improves the lot of griefers, then the surface area you're providing them to attack everyone else will be exponentially larger than the defensible area of reasonable ideologies you hope to have counter the bad ones.
In other words, all the talk of open ideas is true in a truly open marketplace, but violence tends to fill a vacuum, and in a closed system or especially a new, empty space with experimental tooling, it is entirely possible for bad actors to drive out good ones.