example.tex

\documentclass[tikz]{standalone}
    \usepackage{tikz}
    \usetikzlibrary{graphs,graphdrawing}
    \usegdlibrary{trees}
    \usegdlibrary{layered}
    \definecolor{green}{HTML}{339966} 
    \usepackage{adjustbox}
    \usepackage{varwidth}
    \newcommand{\argmapmaxnodewidth}{15em}
\begin{document}
\begin{tikzpicture}
  [
    umbrella/.style args={#1}{
        draw=none,
        rectangle,
        append after command={
            \pgfextra{%
                \pgfkeysgetvalue{/pgf/outer xsep}{\oxsep}
                \pgfkeysgetvalue{/pgf/outer ysep}{\oysep}
                \begin{pgfinterruptpath}
                    \ifx\\#1\\\else
                        \draw[draw,#1] 
                        ([xshift=-\pgflinewidth,yshift=-2mm]\tikzlastnode.north east) 
                        -- ([xshift=-\pgflinewidth,yshift=-\oysep]\tikzlastnode.north east) 
                        -- ([xshift=0,yshift=-\oysep]\tikzlastnode.north west) 
                        -- ([xshift=0,yshift=-2mm]\tikzlastnode.north west);
                    \fi
                \end{pgfinterruptpath}
            }
        }
    },
    claim/.style={draw, black, very thin,
       execute at begin node={\begin{varwidth}{\argmapmaxnodewidth}},
       execute at end node={\end{varwidth}}
    },
    supporting/.style={umbrella={green,very thick}},
    supportingedge/.style={green,very thick},
    opposing/.style={umbrella={red, very thick}},
    opposingedge/.style={red,very thick},
    implicit/.style={dashed}
  ]
  \pgfsetcornersarced{\pgfpoint{.5mm}{.5mm}}  \graph [layered layout, grow=down, tail anchor=center, head anchor=center]
  {
    c1/"Brunellus is irrational
"[claim]
      --[opposingedge]
      r2/"" [opposing] // [ tree layout ] {
        c3/"Brunellus studied in Paris.
"[claim],
        c4/"Most who study in Paris are rational.
"[claim, implicit],
      },
    c1/"Brunellus is irrational
"[claim]
      --[supportingedge]
      r5/"" [supporting] // [ tree layout ] {
        c6/"All donkeys are irrational.
"[claim],
        c7/"Brunellus is a donkey.
"[claim],
      },
  };
\end{tikzpicture}
\end{document}