Jehovah's Witnesses are absolutely correct for refusing blood transfusions.
A close examination of the wording used at Acts 15:28, 29 shows how important it is for Christians to "abstain from blood":
"For it seemed good to the Holy Spirit and to us to lay upon you no greater burden than these ESSENTIALS ['these necessary things' - RSV]: that you abstain from things sacrificed to idols and from blood and from things strangled and from fornication; if you keep yourselves free from such things, you will do well. Farewell." -Acts 15:28, 29 (NASB)
The wording of the scriptures here does not indicate that this is a relatively unimportant commandment. It says it is "ESSENTIAL".
This command went as far back as Noah:
God said: "Only you shall not eat flesh with its life, that is, its blood." (Gen. 9:4) RSV; Moffatt
Andrew Fuller, viewed as "perhaps the most eminent and influential of Baptist theologians," wrote:
"This, being forbidden to Noah, appears also to have been forbidden to all mankind; nor ought this prohibition to be treated as belonging to the ceremonies of the Jewish dispensation. It was not only enjoined before that dispensation existed, but was enforced upon the Gentile Christians by the decrees of the apostles, Acts XV. 20. . . . Blood is the life, and God seems to claim it as sacred to himself." - The Complete Works of the Rev. Andrew Fuller (1836), p. 751.
For more, see:
How important is it for Christians to "abstain from blood"?
Is the Eating or Drinking of Blood Fundamentally Different From Accepting a Blood Transfusion?