What does Alan Alda's quote of "Your assumptions are your windows to the world. Scrub them off every once in awhile or the light wont come in" mean?

This quote by Alan Alda means that the assumptions that
individuals carry are often tempered by time and specific contingencies.  As time
progresses, individuals have to "check their baggage" and examine their own assumptions
to see if they are relevant to the time setting or if they are outdated.  For example,
there was a time when the education of women settled on the domestic realm or avenues to
enhance physical appearance.  The idea of women being in the position of economic,
political, or social power was unimaginable.  The idea of women playing sports on a
professional or amateur level was inconceivable.  These assumptions  have been "scrubbed
off" over the last four decades because of advances in the cause of women's rights. 
There was a time when AIDS was seen as a "gay disease" and "God's curse."  There was a
time when discussion of AIDS was carried on in hushed settings and government funding
for a cure was inconceivable.  These assumptions have been challenged over the last
three decades of scientific research, public awareness, and political responsibility. 
In these examples, individual "assumptions" needed to be "scrubbed" in order to be
consistent with the times.  It is here where Alda's quote speaks the idea of "checking
one's baggage" to see if their opinions are relevant in the current cultural
setting.