Paul McHugh has a long history of opposing transsexuality, claiming that gender identity and gender preference is malliable.

McHugh makes valid assumptions, because about two-thirds of the population is bisexual and two-thirds are gender-fluid. 

1/6 are inflexibly heterosexual.  Men who would prefer Kellyanne conway to Tatum Channing.  And women who would prefer Donald Trump over Emma Watson.

1/6th are exclusively homosexual and would prefer almost any guy over almost any woman.

The folks in the middle will usually be conformant to cisgender-heterosexual norms if the social pressure is intense enough. 

^{Outdated Research}

Paul McHugh bases his conclusions on surgeries performed by Johns Hopkins university by doctors who based their methods on hand-drawn notes.  From the late 60s to 1972.

There were no WPATH screening, no Standards of care, no therapist before and after surgery.

As a result cross-dressers who were still in the closet were getting "the sex change operation" with zero real life experience. 

Botched Operations

Hopkins operations were notable because the vagina was too far forward, there wasn't enough dilation, and depth was minimal.

There was minimal follow-up so when people DID come back to John's Hopkins for follow-up support, it was usually because they didn't have a support network,  lost jobs, families, and homes.  They also had difficulty in relationships with men because their plumbing was so unnatural. 

New Standards of Care

Today we have WPATH Guidelines and Standards of Care,  candidates for surgery have already been on hormones at least a year and living full time as women for at least two.  Most do therapy or support groups or both.  They have built up an environment that supports them as women even before the operation. There are books about the whole process.

Better research on more subjects

Unlike McHugh, who bases his conclusions on a small group of "dissatisfied customers", the last two decades have provided empirical research on thousands of respondents to over dozen surveys of transgender people ranging from cross-dressers to post-op transsexuals.  Furthermore research on suicide lines, including lines dedicated to serving the transgender community,  have provided insights into those who actually end their lives.

As a result, the diagnosis,  treatment,  and effectiveness of treatment for transgender people has been vastly improved since McHugh retired.

McHugh was treating people with a hammer and punch, modern treatment and diagnosis includes blood tests, CT scans, online training and support, thousands of books and online articles, and better legal protections in many states.

What we do know now is that 2 to 3 million people struggle with gender dysphoria.  Of those, roughly a third are seeking transition in some form.  The most common being hormones and breast modification.  Of those, about a third actually undergo "bottom surgery".  Most MTF transsexuals want the surgery but have obstacles that may take years to overcome.  These include lack of insurance coverage,  shortage of surgeons, medical issues such as weight, and lack of "raw material" needed for penile inversion.

As a result,  those who succeed in completing the surgery are always happy to have the completed operation.

We know that half of all transgender people attempt suicide prior to transition.   Those with unsupportive families and friends are at the highest risk, over 80%.  Of those who attempt suicide, over a third will eventually succeed.   Again,  the highest risk are the most repressed.

Transgender people have higher intelligence and are very good at keeping secrets,  especially their Gender Dysphoria,  if they experience rejection, condemnation,  or lack of support.

90% or more experience harassment, assaults, sexual assaults, and threats BEFORE THEY TRANSITION, most before even telling their own families.

Many have been in traditional therapy and were shut down if they talk about wanting to be the opposite sex.  The result is that the dysphoria gets worse and they stop trusting their therapist. 

McHugh bases his observations on a passive view of a few hundred subjects in clinical summaries.

The findings I'm citing are based on 30 years of active interaction with thousands of transgender people over extended periods.

Right wing groups cite McHugh and the American College of Pediatricians, because both offer outdated studies that support the notion that gays and transsexuals should be subjected to conversion therapy.  A combination of various brainwashing techniques that is marginally effective on bisexual and gender fluid subjects.   The remainder usually end up dead or institutionalized.   The only reason practitioners aren't arrested is because the torture and abuse is done in the name of "Religious Counseling".  Most have no medical credentials at all.