The Democratic Party that you describe is not the Democratic Party of today. A century and a half ago, the Democrats were the right-wing conservatives and the Republicans were the progressives. That has reversed.
The Democratic Party doesn’t support the murder of police officers.
The Democratic Party doesn’t support communism. And no — communism and socialism are not the same thing as we use those terms today.
The Democratic Party is not filled with criminals with “alternate agendas”. You’re thinking of the Republicans.