Fun little game...
Google "Bush" and "Hitler" and see how many results pop up!
https://www.google.com/search?q=%22bush%22+%22hitler%22&rlz=1C1CHFX_enUS457US457&oq=%22bush%22+%22hitler%22&aqs=chrome..69i57j0l5.2721j0j7&sourceid=chrome&espv=210&es_sm=122&ie=UTF-8
A lot! About 24,400,000, in fact. A lot of people compared him to Hitler!
So, no, it isn't racist when they do it to Obama.
I mean, just look at how many links pop up with "Obama" & "Hitler":
https://www.google.com/search?rlz=1C1CHFX_enUS457US457&espv=210&es_sm=122&q=%22obama%22+%22hitler%22&oq=%22obama%22+%22hitler%22&gs_l=serp.3..0i7i30l10.19554.20024.0.20173.5.5.0.0.0.2.115.380.2j2.4.0....0...1c.1.36.serp..3.2.189.SjKu0SXipM4
About 182,000,000 results
Wait. Whoa. 182,000,000! That's 157 MILLION more results.
That's roughly HALF the population of America!
Yeah...they called Bush Hitler. But not near the rate they've called Obama that.
Extremism is NOT a two-way street. It's almost all one way and it certainly takes a hard turn to the right.