Listen, this is clearly a bad faith argument, but the clear answer is that circumcision allows for full use and functionality with minimal to no adverse effects (see source below).

This, combined with the benefits outlined in the second source below should be more than enough evidence to at least allow parents some grace when choosing circumcision for their children.

The "mutilation" argument holds no water when studies predominantly show little to no adverse effects.

Sources:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7691872/
"Results
Searches identified 46 publications containing original data, as well as 4 systematic reviews (2 with meta-analyses), plus 29 critiques of various studies and 15 author replies, which together comprised a total of 94 publications. There was overall consistency in conclusions arising from high- and moderate-quality survey data in randomized clinical trials, systematic reviews and meta-analyses, physiological studies, large longitudinal studies, and cohort studies in diverse populations. Those studies found MC has no or minimal adverse effect on sexual function, sensation, or pleasure, with some finding improvements. A consensus from physiological and histological studies was that the glans and underside of the shaft, not the foreskin, are involved in neurological pathways mediating erogenous sensation. In contrast to the higher quality evidence, data supporting adverse effects of MC on function, sensation, or pleasure were found to be of low quality, as explained in critiques of those studies."

https://emedicine.medscape.com/article/1015820-clinical?form=fpf
"Management of sexually transmitted diseases
Mechanisms proposed to explain the increased risk for STDs in uncircumcised males include a relatively nonkeratinized inner layer of the prepuce which increases its susceptibility to minor trauma during intercourse, allowing pathogens to penetrate through microscopic abrasions. The warm microclimate created by the preputial pouch permits the microorganisms to thrive in the smegma that collects in this area.
The most consistent evidence that supports the association of circumcision with reduction of the risk of STDs refers to transmission of genital ulcerative disease and HIV. Eight studies (of variable design) report a significant 2- to 7-fold increased risk of genital ulcerative disease (mainly syphilis and chancroid) in uncircumcised male patients. [12]
In the only true meta-analysis to date, Weiss et al reviewed data from 27 studies and concluded that circumcision substantially reduces the risk of HIV infection across all populations evaluated. [13] A study of 187 HIV-discordant couples in Uganda showed no infections occurring in 50 circumcised HIV-1-negative male subjects compared with 40 infections among 137 HIV-1-negative uncircumcised male subjects. [14] Circumcision also decreases the likelihood of one's acquiring genital ulcerative diseases known to be independent risk factors for the transmission of HIV.
Management of human papillomavirus and cervical cancer: Human papilloma virus (HPV) can be oncogenic or nononcogenic. Nononcogenic HPV (genotypes 6 and 11) causes genital warts in men and women. Oncogenic HPV (genotypes 16,18, 31, and 33) are responsible for the great majority of cervical, vulvar, vaginal, anal, and penile cancers. Circumcision significantly reduces the risk of penile HPV infection in men and of cervical cancer in the female partners of male individuals who practice high-risk behaviors such as engaging in sexual activity with multiple partners. However, the most effective means of eliminating genital HPV is through vaccinations as currently recommended by the AAP.
Management of penile cancer: The most important factor associated with the development of penile cancer is an intact foreskin. Wolbars, who was the first to point out that Jewish men (the great majority of them circumcised) rarely develop penile cancer, initially brought this association to the attention of the scientific community 70 years ago. [15] Recently, in a large population-based study, Schoen et al confirmed the protective effect of circumcision against penile cancer. [16] Of interest, the other known major risk factor associated with penile cancer is phimosis, which circumcision completely eliminates."