What a horribly ignorant thing to say. The actual biggest “export” and contribution that Salvadorans in the US bring in terms of the economy is labor. As a matter of fact, a higher proportion of Salvadorans in America participate in the labor force than the general U.S. population by about 11% (here is a source).
And if you must know, only 10% of gang members in El Salvador reported ever stepping foot in the United States per this source from 2016 whose work was conducted with support from the US Department of State. This makes sense as the vast majority of Salvadoran immigrants are coming to the US to escape violence and try to build a better, safer life.
When people say that the majority of Salvadorans coming over are gang members, or criminals, or rapists or whatever, they are ignoring actual facts and percentages and instead are just repeating hateful rhetoric over and over without actually looking at facts.