Wouldn't this amendment violate my first amendment rights?

Absolutely not. We are not talking about regulating speech. We are talking about curtailing offensive conduct. Under the amendment, those who disagree with government would still have the right to criticize elected officials, the government or the flag itself, by word or in writing. During the 100 year span when flag desecration was illegal, no one's first amendment rights were in jeopardy and no one believed they were.