First let's start with an estimate of how many of these folks there actually are in the US. Anti-Choice and Pro-Death split close to 50/50, so we can estimate that there are somewhere on the order of 150 Million anti-choicers. Note, for the purposes of this discussion, I'm using the more derogatory name for both sides.
The article below by Gallup indicates that a little less than half has self-identified as pro-life, but only between a quarter and a third supports abortion for any reason. By many people's definitions, this would make 2/3 to 3/4 of the population anti choice. But we'll go by their self-description on the poll where they were asked to make a binary choice.
http://www.gallup.com/poll/118399/more-americans-pro-life-than-pro-choice-first-time.aspx
This shouldn't be terribly surprising. The pro-deathers have generally had to defend their gains and make advances through the courts, something they wouldn't have to do if they had a majority.
Now, a lot of attention gets paid to anti-abortion violence
http://en.wikipedia.org/wiki/Anti-abortion_violence
Since Roe v Wade in 1973, there have been 8 murders of abortionists, abortion employees, or escorts of same. On Wikipedia you can read about every single case, making this a terribly accurate statistic---it is an actual enumeration.
From our friends in the FBI's UCR---they've made their stats available back to 1960 through
http://www.ucrdatatool.gov/
Estimated murder rate * Year United States-Total
--------------------------------------------------------------------------------
1973 9.4
1974 9.8
1975 9.6
1976 8.7
1977 8.8
1978 9.0
1979 9.8
1980 10.2
1981 9.8
1982 9.1
1983 8.3
1984 7.9
1985 8.0
1986 8.6
1987 8.3
1988 8.5
1989 8.7
1990 9.4
1991 9.8
1992 9.3
1993 9.5
1994 9.0
1995 8.2
1996 7.4
1997 6.8
1998 6.3
1999 5.7
2000 5.5
2001 5.6
2002 5.6
2003 5.7
2004 5.5
2005 5.6
2006 5.7
2007 5.6
2008 5.4
2009 5.0
Notes: National or state offense totals are based on data from all reporting agencies and estimates for unreported areas.
* Rates are the number of reported offenses per 100,000 population
United States-Total -
The 168 murder and nonnegligent homicides that occurred as a result of the bombing of the Alfred P. Murrah Federal Building in Oklahoma City in 1995 are included in the national estimate.
The 2,823 murder and nonnegligent homicides that occurred as a result of the events of September 11, 2001, are not included in the national estimates.
Sources: FBI, Uniform Crime Reports as prepared by the National Archive of Criminal Justice Data
From this we can see that the homicide rate per 100k is between about 5 and 10 throughout the period of interest. A reasonable average estimate might be 7.5 per 100k. We're also talking about a period of approximately 37 years. So the expected number of homicides per 100k people over this span of time would be about 7.5*37, or about 277.5.
Now, let's further assume that anti-choicers are like motorcycle gangs---i.e. only 1% are HARDCORE. That gives us a radical anti-choice population of 1.5 Million. We'll assume the other 148.5 million are just poseurs.
So if we assume that this radical anti-choice population is as murderous on average as the average American, we'd expect them to produce 277.5*15, or 4162.5 murders. If we further assume that this group's murderous rage has only a tithe directed at abortionists and their collaterals, we'd expect to see 416 murders. These are terribly weak assumptions when one considers them---I mean---only 1% of the group being considered at all, only having a murder rate equal to the population as a whole, and only directing 10% of their total red-handed wrath at their supposedly hated foes?
So how many abortionists and minions of abortionists did they actually kill again?
8.
That's it, less than 1/50 of what we'd expect even under these ridiculously low assumptions.
Clearly this group is a LOT less violent than they're given credit for being. One would almost think there was an organized media effort to skew the public's histogram of perceived violence by groups.