Antisemitism: What is it? How is it being Weaponized?

How strange that we live in an era where we can criticize our own country, and other countries, with one exception;  if we criticize Israel, even for actions that are clearly war crimes, crimes against humanity or Apartheid style government, we can easily find ourselves being accused of antisemitism, and perhaps  then enduring lasting consequences.  Students who protest US military weapons  being freely given to Israel, may lose their student visas, or be removed from their educational program. Boycotts, divestments and sanctions, a common way to approach  economic pressure  toward countries and businesses are once again singled out as antisemitism if applied to Israel.

Examples:

How has American Free Speech become so compromised? How have two unrelated thoughts, antisemitism and Israeli government criticism become so intimately connected and to create so much potential for harm to people who are using their first amendment rights? 

What's more, legislation is being proposed and in some cases implemented on state, local and even federal level to make these falsely conflated concepts of criticism toward Israel  with antisemitism into law, essentially making criticism of the criminal acts of Israel illegal and punishable. A bill passed the House  but not the Senate, that would have adopted this definition.

Background