Unlike many other countries, our legal system is open for all to witness, from beginning to end. State and federal executions always have witnesses: prison officials, prosecutors, defense attorneys, victims and/or their families, the press, and even a few citizens.
The county I live in frequently uses video arraignment hearings instead of in person, for those charged with violent crimes. In keeping with hearings being open to the public, the county provides those videos to the local news stations to broadcast.
An execution streamed over the Internet is no different.
No one is celebrating the death of a violent terrorist. The execution is a reminder of both the evil that exists in the world, and the justice that triumphs over it.