There are philosophers, religious individuals and those, religious or not, who believe that sex is unitive (via marriage) and for conception and therefore contraception is an immoral and unnatural action that goes against that principle of denying a human life the right to exist and therefore should be banned (a return to the Comstock laws once the relevant Supreme Court historic decisions are overturned like Roe v Wade was for abortion). As far as these groups are concerned, contraception is pre-abortion and just as immoral and righteous to ban as abortion. It would form part of the anti-vice pushback and counteraction to what liberals have been implementing in the last few decades in terms of sexual liberation, not just against abortion, contraception, promiscuity and pornography but other forms of vice including alcohol, smoking and gambling.

Ironically, the people saying pro-life supporters are also pro-birth control and contraception are left leaning outlets! Maybe hoping that the right wing don't go for contraception as well as abortion as was the case in the past.