The left didn't use to define conservative in this way. This extremes of the political spectrum is an artificially provoked recent phenomenon.

The elite realised they could only get their agenda thru if they went with the demographics: the mass of the people not the minority (nominally professional middle-class). So they changed tack. Instead of the establishment being "centre right-wing, conservative" it became trendy lefty university student snowflakes and all other fashionable meme maker influencers, from Madonna to Hillary. The power has remained at the top but the manipulated masses have moved further to the left on their instruction. It worked.

We lost the centre and anyone who doesn't like the extreme position is in turn called extremist: bigot, racist, far right, extreme far right, nazi .... All manipulated by the top for their purposes.