Except in some Southern states where TSO might speak Spanish, the TSA is essentially an English only outfit. If speaking with a BDO is a mandatory part of boarding a plane, then one of two conditions must be met.

One, since TSOs are English only, then speaking English must be made a condition for all pax who want to fly.

Or, two, TSA must make a reasonable effort to have speakers of all the languages they would reasonably expect to see daily at their checkpoint. Otherwise a terrorist just pretends not to speak English and avoids detection. For example, at the TBIT at LAX the TSA would need speakers of all the Asian languages at the checkpoint. I am sure every day elderly Asian who speak no English come to the US to visit their grandkids.

If speaking to a BDO is a preconditon to fly, it is up to the TSA to speak the pax's language, not the other way around. Otherwise, there can be no requirement for a pax to talk to them.